1 // SPDX-License-Identifier: GPL-2.0-only
5 * Runtime locking correctness validator
7 * Started by Ingo Molnar:
9 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
12 * this code maps all the lock dependencies as they occur in a live kernel
13 * and will warn about the following classes of locking bugs:
15 * - lock inversion scenarios
16 * - circular lock dependencies
17 * - hardirq/softirq safe/unsafe locking bugs
19 * Bugs are reported even if the current locking scenario does not cause
20 * any deadlock at this point.
22 * I.e. if anytime in the past two locks were taken in a different order,
23 * even if it happened for another task, even if those were different
24 * locks (but of the same class as this lock), this code will detect it.
26 * Thanks to Arjan van de Ven for coming up with the initial idea of
27 * mapping lock dependencies runtime.
29 #define DISABLE_BRANCH_PROFILING
30 #include <linux/mutex.h>
31 #include <linux/sched.h>
32 #include <linux/sched/clock.h>
33 #include <linux/sched/task.h>
34 #include <linux/sched/mm.h>
35 #include <linux/delay.h>
36 #include <linux/module.h>
37 #include <linux/proc_fs.h>
38 #include <linux/seq_file.h>
39 #include <linux/spinlock.h>
40 #include <linux/kallsyms.h>
41 #include <linux/interrupt.h>
42 #include <linux/stacktrace.h>
43 #include <linux/debug_locks.h>
44 #include <linux/irqflags.h>
45 #include <linux/utsname.h>
46 #include <linux/hash.h>
47 #include <linux/ftrace.h>
48 #include <linux/stringify.h>
49 #include <linux/bitmap.h>
50 #include <linux/bitops.h>
51 #include <linux/gfp.h>
52 #include <linux/random.h>
53 #include <linux/jhash.h>
54 #include <linux/nmi.h>
55 #include <linux/rcupdate.h>
56 #include <linux/kprobes.h>
57 #include <linux/lockdep.h>
59 #include <asm/sections.h>
61 #include "lockdep_internals.h"
63 #include <trace/events/lock.h>
65 #ifdef CONFIG_PROVE_LOCKING
66 static int prove_locking = 1;
67 module_param(prove_locking, int, 0644);
69 #define prove_locking 0
72 #ifdef CONFIG_LOCK_STAT
73 static int lock_stat = 1;
74 module_param(lock_stat, int, 0644);
80 static struct ctl_table kern_lockdep_table[] = {
81 #ifdef CONFIG_PROVE_LOCKING
83 .procname = "prove_locking",
84 .data = &prove_locking,
85 .maxlen = sizeof(int),
87 .proc_handler = proc_dointvec,
89 #endif /* CONFIG_PROVE_LOCKING */
90 #ifdef CONFIG_LOCK_STAT
92 .procname = "lock_stat",
94 .maxlen = sizeof(int),
96 .proc_handler = proc_dointvec,
98 #endif /* CONFIG_LOCK_STAT */
102 static __init int kernel_lockdep_sysctls_init(void)
104 register_sysctl_init("kernel", kern_lockdep_table);
107 late_initcall(kernel_lockdep_sysctls_init);
108 #endif /* CONFIG_SYSCTL */
110 DEFINE_PER_CPU(unsigned int, lockdep_recursion);
111 EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
113 static __always_inline bool lockdep_enabled(void)
118 if (this_cpu_read(lockdep_recursion))
121 if (current->lockdep_recursion)
128 * lockdep_lock: protects the lockdep graph, the hashes and the
129 * class/list/hash allocators.
131 * This is one of the rare exceptions where it's justified
132 * to use a raw spinlock - we really dont want the spinlock
133 * code to recurse back into the lockdep code...
135 static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
136 static struct task_struct *__owner;
138 static inline void lockdep_lock(void)
140 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
142 __this_cpu_inc(lockdep_recursion);
143 arch_spin_lock(&__lock);
147 static inline void lockdep_unlock(void)
149 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
151 if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
155 arch_spin_unlock(&__lock);
156 __this_cpu_dec(lockdep_recursion);
159 static inline bool lockdep_assert_locked(void)
161 return DEBUG_LOCKS_WARN_ON(__owner != current);
164 static struct task_struct *lockdep_selftest_task_struct;
167 static int graph_lock(void)
171 * Make sure that if another CPU detected a bug while
172 * walking the graph we dont change it (while the other
173 * CPU is busy printing out stuff with the graph lock
183 static inline void graph_unlock(void)
189 * Turn lock debugging off and return with 0 if it was off already,
190 * and also release the graph lock:
192 static inline int debug_locks_off_graph_unlock(void)
194 int ret = debug_locks_off();
201 unsigned long nr_list_entries;
202 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
203 static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
206 * All data structures here are protected by the global debug_lock.
208 * nr_lock_classes is the number of elements of lock_classes[] that is
211 #define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
212 #define KEYHASH_SIZE (1UL << KEYHASH_BITS)
213 static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
214 unsigned long nr_lock_classes;
215 unsigned long nr_zapped_classes;
216 unsigned long max_lock_class_idx;
217 struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
218 DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
220 static inline struct lock_class *hlock_class(struct held_lock *hlock)
222 unsigned int class_idx = hlock->class_idx;
224 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
227 if (!test_bit(class_idx, lock_classes_in_use)) {
229 * Someone passed in garbage, we give up.
231 DEBUG_LOCKS_WARN_ON(1);
236 * At this point, if the passed hlock->class_idx is still garbage,
237 * we just have to live with it
239 return lock_classes + class_idx;
242 #ifdef CONFIG_LOCK_STAT
243 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
245 static inline u64 lockstat_clock(void)
247 return local_clock();
250 static int lock_point(unsigned long points[], unsigned long ip)
254 for (i = 0; i < LOCKSTAT_POINTS; i++) {
255 if (points[i] == 0) {
266 static void lock_time_inc(struct lock_time *lt, u64 time)
271 if (time < lt->min || !lt->nr)
278 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
283 if (src->max > dst->max)
286 if (src->min < dst->min || !dst->nr)
289 dst->total += src->total;
293 struct lock_class_stats lock_stats(struct lock_class *class)
295 struct lock_class_stats stats;
298 memset(&stats, 0, sizeof(struct lock_class_stats));
299 for_each_possible_cpu(cpu) {
300 struct lock_class_stats *pcs =
301 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
303 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
304 stats.contention_point[i] += pcs->contention_point[i];
306 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
307 stats.contending_point[i] += pcs->contending_point[i];
309 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
310 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
312 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
313 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
315 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
316 stats.bounces[i] += pcs->bounces[i];
322 void clear_lock_stats(struct lock_class *class)
326 for_each_possible_cpu(cpu) {
327 struct lock_class_stats *cpu_stats =
328 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
330 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
332 memset(class->contention_point, 0, sizeof(class->contention_point));
333 memset(class->contending_point, 0, sizeof(class->contending_point));
336 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
338 return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
341 static void lock_release_holdtime(struct held_lock *hlock)
343 struct lock_class_stats *stats;
349 holdtime = lockstat_clock() - hlock->holdtime_stamp;
351 stats = get_lock_stats(hlock_class(hlock));
353 lock_time_inc(&stats->read_holdtime, holdtime);
355 lock_time_inc(&stats->write_holdtime, holdtime);
358 static inline void lock_release_holdtime(struct held_lock *hlock)
364 * We keep a global list of all lock classes. The list is only accessed with
365 * the lockdep spinlock lock held. free_lock_classes is a list with free
366 * elements. These elements are linked together by the lock_entry member in
369 static LIST_HEAD(all_lock_classes);
370 static LIST_HEAD(free_lock_classes);
373 * struct pending_free - information about data structures about to be freed
374 * @zapped: Head of a list with struct lock_class elements.
375 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
376 * are about to be freed.
378 struct pending_free {
379 struct list_head zapped;
380 DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
384 * struct delayed_free - data structures used for delayed freeing
386 * A data structure for delayed freeing of data structures that may be
387 * accessed by RCU readers at the time these were freed.
389 * @rcu_head: Used to schedule an RCU callback for freeing data structures.
390 * @index: Index of @pf to which freed data structures are added.
391 * @scheduled: Whether or not an RCU callback has been scheduled.
392 * @pf: Array with information about data structures about to be freed.
394 static struct delayed_free {
395 struct rcu_head rcu_head;
398 struct pending_free pf[2];
402 * The lockdep classes are in a hash-table as well, for fast lookup:
404 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
405 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
406 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
407 #define classhashentry(key) (classhash_table + __classhashfn((key)))
409 static struct hlist_head classhash_table[CLASSHASH_SIZE];
412 * We put the lock dependency chains into a hash-table as well, to cache
415 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
416 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
417 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
418 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
420 static struct hlist_head chainhash_table[CHAINHASH_SIZE];
423 * the id of held_lock
425 static inline u16 hlock_id(struct held_lock *hlock)
427 BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
429 return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
432 static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
434 return hlock_id & (MAX_LOCKDEP_KEYS - 1);
438 * The hash key of the lock dependency chains is a hash itself too:
439 * it's a hash of all locks taken up to that lock, including that lock.
440 * It's a 64-bit hash, because it's important for the keys to be
443 static inline u64 iterate_chain_key(u64 key, u32 idx)
445 u32 k0 = key, k1 = key >> 32;
447 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
449 return k0 | (u64)k1 << 32;
452 void lockdep_init_task(struct task_struct *task)
454 task->lockdep_depth = 0; /* no locks held yet */
455 task->curr_chain_key = INITIAL_CHAIN_KEY;
456 task->lockdep_recursion = 0;
459 static __always_inline void lockdep_recursion_inc(void)
461 __this_cpu_inc(lockdep_recursion);
464 static __always_inline void lockdep_recursion_finish(void)
466 if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
467 __this_cpu_write(lockdep_recursion, 0);
470 void lockdep_set_selftest_task(struct task_struct *task)
472 lockdep_selftest_task_struct = task;
476 * Debugging switches:
480 #define VERY_VERBOSE 0
483 # define HARDIRQ_VERBOSE 1
484 # define SOFTIRQ_VERBOSE 1
486 # define HARDIRQ_VERBOSE 0
487 # define SOFTIRQ_VERBOSE 0
490 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
492 * Quick filtering for interesting events:
494 static int class_filter(struct lock_class *class)
498 if (class->name_version == 1 &&
499 !strcmp(class->name, "lockname"))
501 if (class->name_version == 1 &&
502 !strcmp(class->name, "&struct->lockfield"))
505 /* Filter everything else. 1 would be to allow everything else */
510 static int verbose(struct lock_class *class)
513 return class_filter(class);
518 static void print_lockdep_off(const char *bug_msg)
520 printk(KERN_DEBUG "%s\n", bug_msg);
521 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
522 #ifdef CONFIG_LOCK_STAT
523 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
527 unsigned long nr_stack_trace_entries;
529 #ifdef CONFIG_PROVE_LOCKING
531 * struct lock_trace - single stack backtrace
532 * @hash_entry: Entry in a stack_trace_hash[] list.
533 * @hash: jhash() of @entries.
534 * @nr_entries: Number of entries in @entries.
535 * @entries: Actual stack backtrace.
538 struct hlist_node hash_entry;
541 unsigned long entries[] __aligned(sizeof(unsigned long));
543 #define LOCK_TRACE_SIZE_IN_LONGS \
544 (sizeof(struct lock_trace) / sizeof(unsigned long))
546 * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
548 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
549 static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
551 static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
553 return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
554 memcmp(t1->entries, t2->entries,
555 t1->nr_entries * sizeof(t1->entries[0])) == 0;
558 static struct lock_trace *save_trace(void)
560 struct lock_trace *trace, *t2;
561 struct hlist_head *hash_head;
565 BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
566 BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
568 trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
569 max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
570 LOCK_TRACE_SIZE_IN_LONGS;
572 if (max_entries <= 0) {
573 if (!debug_locks_off_graph_unlock())
576 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
581 trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
583 hash = jhash(trace->entries, trace->nr_entries *
584 sizeof(trace->entries[0]), 0);
586 hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
587 hlist_for_each_entry(t2, hash_head, hash_entry) {
588 if (traces_identical(trace, t2))
591 nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
592 hlist_add_head(&trace->hash_entry, hash_head);
597 /* Return the number of stack traces in the stack_trace[] array. */
598 u64 lockdep_stack_trace_count(void)
600 struct lock_trace *trace;
604 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
605 hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
613 /* Return the number of stack hash chains that have at least one stack trace. */
614 u64 lockdep_stack_hash_count(void)
619 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
620 if (!hlist_empty(&stack_trace_hash[i]))
627 unsigned int nr_hardirq_chains;
628 unsigned int nr_softirq_chains;
629 unsigned int nr_process_chains;
630 unsigned int max_lockdep_depth;
632 #ifdef CONFIG_DEBUG_LOCKDEP
634 * Various lockdep statistics:
636 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
639 #ifdef CONFIG_PROVE_LOCKING
644 #define __USAGE(__STATE) \
645 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
646 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
647 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
648 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
650 static const char *usage_str[] =
652 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
653 #include "lockdep_states.h"
655 [LOCK_USED] = "INITIAL USE",
656 [LOCK_USED_READ] = "INITIAL READ USE",
657 /* abused as string storage for verify_lock_unused() */
658 [LOCK_USAGE_STATES] = "IN-NMI",
662 const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
664 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
667 static inline unsigned long lock_flag(enum lock_usage_bit bit)
672 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
675 * The usage character defaults to '.' (i.e., irqs disabled and not in
676 * irq context), which is the safest usage category.
681 * The order of the following usage checks matters, which will
682 * result in the outcome character as follows:
684 * - '+': irq is enabled and not in irq context
685 * - '-': in irq context and irq is disabled
686 * - '?': in irq context and irq is enabled
688 if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
690 if (class->usage_mask & lock_flag(bit))
692 } else if (class->usage_mask & lock_flag(bit))
698 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
702 #define LOCKDEP_STATE(__STATE) \
703 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
704 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
705 #include "lockdep_states.h"
711 static void __print_lock_name(struct lock_class *class)
713 char str[KSYM_NAME_LEN];
718 name = __get_key_name(class->key, str);
719 printk(KERN_CONT "%s", name);
721 printk(KERN_CONT "%s", name);
722 if (class->name_version > 1)
723 printk(KERN_CONT "#%d", class->name_version);
725 printk(KERN_CONT "/%d", class->subclass);
729 static void print_lock_name(struct lock_class *class)
731 char usage[LOCK_USAGE_CHARS];
733 get_usage_chars(class, usage);
735 printk(KERN_CONT " (");
736 __print_lock_name(class);
737 printk(KERN_CONT "){%s}-{%d:%d}", usage,
738 class->wait_type_outer ?: class->wait_type_inner,
739 class->wait_type_inner);
742 static void print_lockdep_cache(struct lockdep_map *lock)
745 char str[KSYM_NAME_LEN];
749 name = __get_key_name(lock->key->subkeys, str);
751 printk(KERN_CONT "%s", name);
754 static void print_lock(struct held_lock *hlock)
757 * We can be called locklessly through debug_show_all_locks() so be
758 * extra careful, the hlock might have been released and cleared.
760 * If this indeed happens, lets pretend it does not hurt to continue
761 * to print the lock unless the hlock class_idx does not point to a
762 * registered class. The rationale here is: since we don't attempt
763 * to distinguish whether we are in this situation, if it just
764 * happened we can't count on class_idx to tell either.
766 struct lock_class *lock = hlock_class(hlock);
769 printk(KERN_CONT "<RELEASED>\n");
773 printk(KERN_CONT "%px", hlock->instance);
774 print_lock_name(lock);
775 printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
778 static void lockdep_print_held_locks(struct task_struct *p)
780 int i, depth = READ_ONCE(p->lockdep_depth);
783 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
785 printk("%d lock%s held by %s/%d:\n", depth,
786 depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
788 * It's not reliable to print a task's held locks if it's not sleeping
789 * and it's not the current task.
791 if (p != current && task_is_running(p))
793 for (i = 0; i < depth; i++) {
795 print_lock(p->held_locks + i);
799 static void print_kernel_ident(void)
801 printk("%s %.*s %s\n", init_utsname()->release,
802 (int)strcspn(init_utsname()->version, " "),
803 init_utsname()->version,
807 static int very_verbose(struct lock_class *class)
810 return class_filter(class);
816 * Is this the address of a static object:
820 * Check if an address is part of freed initmem. After initmem is freed,
821 * memory can be allocated from it, and such allocations would then have
822 * addresses within the range [_stext, _end].
824 #ifndef arch_is_kernel_initmem_freed
825 static int arch_is_kernel_initmem_freed(unsigned long addr)
827 if (system_state < SYSTEM_FREEING_INITMEM)
830 return init_section_contains((void *)addr, 1);
834 static int static_obj(const void *obj)
836 unsigned long start = (unsigned long) &_stext,
837 end = (unsigned long) &_end,
838 addr = (unsigned long) obj;
840 if (arch_is_kernel_initmem_freed(addr))
846 if ((addr >= start) && (addr < end))
850 * in-kernel percpu var?
852 if (is_kernel_percpu_address(addr))
856 * module static or percpu var?
858 return is_module_address(addr) || is_module_percpu_address(addr);
863 * To make lock name printouts unique, we calculate a unique
864 * class->name_version generation counter. The caller must hold the graph
867 static int count_matching_names(struct lock_class *new_class)
869 struct lock_class *class;
872 if (!new_class->name)
875 list_for_each_entry(class, &all_lock_classes, lock_entry) {
876 if (new_class->key - new_class->subclass == class->key)
877 return class->name_version;
878 if (class->name && !strcmp(class->name, new_class->name))
879 count = max(count, class->name_version);
885 /* used from NMI context -- must be lockless */
886 static noinstr struct lock_class *
887 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
889 struct lockdep_subclass_key *key;
890 struct hlist_head *hash_head;
891 struct lock_class *class;
893 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
894 instrumentation_begin();
897 "BUG: looking up invalid subclass: %u\n", subclass);
899 "turning off the locking correctness validator.\n");
901 instrumentation_end();
906 * If it is not initialised then it has never been locked,
907 * so it won't be present in the hash table.
909 if (unlikely(!lock->key))
913 * NOTE: the class-key must be unique. For dynamic locks, a static
914 * lock_class_key variable is passed in through the mutex_init()
915 * (or spin_lock_init()) call - which acts as the key. For static
916 * locks we use the lock object itself as the key.
918 BUILD_BUG_ON(sizeof(struct lock_class_key) >
919 sizeof(struct lockdep_map));
921 key = lock->key->subkeys + subclass;
923 hash_head = classhashentry(key);
926 * We do an RCU walk of the hash, see lockdep_free_key_range().
928 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
931 hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
932 if (class->key == key) {
934 * Huh! same key, different name? Did someone trample
935 * on some memory? We're most confused.
937 WARN_ONCE(class->name != lock->name &&
938 lock->key != &__lockdep_no_validate__,
939 "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n",
940 lock->name, lock->key, class->name);
949 * Static locks do not have their class-keys yet - for them the key is
950 * the lock object itself. If the lock is in the per cpu area, the
951 * canonical address of the lock (per cpu offset removed) is used.
953 static bool assign_lock_key(struct lockdep_map *lock)
955 unsigned long can_addr, addr = (unsigned long)lock;
959 * lockdep_free_key_range() assumes that struct lock_class_key
960 * objects do not overlap. Since we use the address of lock
961 * objects as class key for static objects, check whether the
962 * size of lock_class_key objects does not exceed the size of
963 * the smallest lock object.
965 BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
968 if (__is_kernel_percpu_address(addr, &can_addr))
969 lock->key = (void *)can_addr;
970 else if (__is_module_percpu_address(addr, &can_addr))
971 lock->key = (void *)can_addr;
972 else if (static_obj(lock))
973 lock->key = (void *)lock;
975 /* Debug-check: all keys must be persistent! */
977 pr_err("INFO: trying to register non-static key.\n");
978 pr_err("The code is fine but needs lockdep annotation, or maybe\n");
979 pr_err("you didn't initialize this object before use?\n");
980 pr_err("turning off the locking correctness validator.\n");
988 #ifdef CONFIG_DEBUG_LOCKDEP
990 /* Check whether element @e occurs in list @h */
991 static bool in_list(struct list_head *e, struct list_head *h)
995 list_for_each(f, h) {
1004 * Check whether entry @e occurs in any of the locks_after or locks_before
1007 static bool in_any_class_list(struct list_head *e)
1009 struct lock_class *class;
1012 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1013 class = &lock_classes[i];
1014 if (in_list(e, &class->locks_after) ||
1015 in_list(e, &class->locks_before))
1021 static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
1023 struct lock_list *e;
1025 list_for_each_entry(e, h, entry) {
1026 if (e->links_to != c) {
1027 printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
1029 (unsigned long)(e - list_entries),
1030 e->links_to && e->links_to->name ?
1031 e->links_to->name : "(?)",
1032 e->class && e->class->name ? e->class->name :
1040 #ifdef CONFIG_PROVE_LOCKING
1041 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1044 static bool check_lock_chain_key(struct lock_chain *chain)
1046 #ifdef CONFIG_PROVE_LOCKING
1047 u64 chain_key = INITIAL_CHAIN_KEY;
1050 for (i = chain->base; i < chain->base + chain->depth; i++)
1051 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
1053 * The 'unsigned long long' casts avoid that a compiler warning
1054 * is reported when building tools/lib/lockdep.
1056 if (chain->chain_key != chain_key) {
1057 printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
1058 (unsigned long long)(chain - lock_chains),
1059 (unsigned long long)chain->chain_key,
1060 (unsigned long long)chain_key);
1067 static bool in_any_zapped_class_list(struct lock_class *class)
1069 struct pending_free *pf;
1072 for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
1073 if (in_list(&class->lock_entry, &pf->zapped))
1080 static bool __check_data_structures(void)
1082 struct lock_class *class;
1083 struct lock_chain *chain;
1084 struct hlist_head *head;
1085 struct lock_list *e;
1088 /* Check whether all classes occur in a lock list. */
1089 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1090 class = &lock_classes[i];
1091 if (!in_list(&class->lock_entry, &all_lock_classes) &&
1092 !in_list(&class->lock_entry, &free_lock_classes) &&
1093 !in_any_zapped_class_list(class)) {
1094 printk(KERN_INFO "class %px/%s is not in any class list\n",
1095 class, class->name ? : "(?)");
1100 /* Check whether all classes have valid lock lists. */
1101 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1102 class = &lock_classes[i];
1103 if (!class_lock_list_valid(class, &class->locks_before))
1105 if (!class_lock_list_valid(class, &class->locks_after))
1109 /* Check the chain_key of all lock chains. */
1110 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1111 head = chainhash_table + i;
1112 hlist_for_each_entry_rcu(chain, head, entry) {
1113 if (!check_lock_chain_key(chain))
1119 * Check whether all list entries that are in use occur in a class
1122 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1123 e = list_entries + i;
1124 if (!in_any_class_list(&e->entry)) {
1125 printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1126 (unsigned int)(e - list_entries),
1127 e->class->name ? : "(?)",
1128 e->links_to->name ? : "(?)");
1134 * Check whether all list entries that are not in use do not occur in
1135 * a class lock list.
1137 for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1138 e = list_entries + i;
1139 if (in_any_class_list(&e->entry)) {
1140 printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1141 (unsigned int)(e - list_entries),
1142 e->class && e->class->name ? e->class->name :
1144 e->links_to && e->links_to->name ?
1145 e->links_to->name : "(?)");
1153 int check_consistency = 0;
1154 module_param(check_consistency, int, 0644);
1156 static void check_data_structures(void)
1158 static bool once = false;
1160 if (check_consistency && !once) {
1161 if (!__check_data_structures()) {
1168 #else /* CONFIG_DEBUG_LOCKDEP */
1170 static inline void check_data_structures(void) { }
1172 #endif /* CONFIG_DEBUG_LOCKDEP */
1174 static void init_chain_block_buckets(void);
1177 * Initialize the lock_classes[] array elements, the free_lock_classes list
1178 * and also the delayed_free structure.
1180 static void init_data_structures_once(void)
1182 static bool __read_mostly ds_initialized, rcu_head_initialized;
1185 if (likely(rcu_head_initialized))
1188 if (system_state >= SYSTEM_SCHEDULING) {
1189 init_rcu_head(&delayed_free.rcu_head);
1190 rcu_head_initialized = true;
1196 ds_initialized = true;
1198 INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1199 INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1201 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1202 list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1203 INIT_LIST_HEAD(&lock_classes[i].locks_after);
1204 INIT_LIST_HEAD(&lock_classes[i].locks_before);
1206 init_chain_block_buckets();
1209 static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1211 unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1213 return lock_keys_hash + hash;
1216 /* Register a dynamically allocated key. */
1217 void lockdep_register_key(struct lock_class_key *key)
1219 struct hlist_head *hash_head;
1220 struct lock_class_key *k;
1221 unsigned long flags;
1223 if (WARN_ON_ONCE(static_obj(key)))
1225 hash_head = keyhashentry(key);
1227 raw_local_irq_save(flags);
1230 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1231 if (WARN_ON_ONCE(k == key))
1234 hlist_add_head_rcu(&key->hash_entry, hash_head);
1238 raw_local_irq_restore(flags);
1240 EXPORT_SYMBOL_GPL(lockdep_register_key);
1242 /* Check whether a key has been registered as a dynamic key. */
1243 static bool is_dynamic_key(const struct lock_class_key *key)
1245 struct hlist_head *hash_head;
1246 struct lock_class_key *k;
1249 if (WARN_ON_ONCE(static_obj(key)))
1253 * If lock debugging is disabled lock_keys_hash[] may contain
1254 * pointers to memory that has already been freed. Avoid triggering
1255 * a use-after-free in that case by returning early.
1260 hash_head = keyhashentry(key);
1263 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1275 * Register a lock's class in the hash-table, if the class is not present
1276 * yet. Otherwise we look it up. We cache the result in the lock object
1277 * itself, so actual lookup of the hash should be once per lock object.
1279 static struct lock_class *
1280 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1282 struct lockdep_subclass_key *key;
1283 struct hlist_head *hash_head;
1284 struct lock_class *class;
1287 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1289 class = look_up_lock_class(lock, subclass);
1291 goto out_set_class_cache;
1294 if (!assign_lock_key(lock))
1296 } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1300 key = lock->key->subkeys + subclass;
1301 hash_head = classhashentry(key);
1303 if (!graph_lock()) {
1307 * We have to do the hash-walk again, to avoid races
1310 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1311 if (class->key == key)
1312 goto out_unlock_set;
1315 init_data_structures_once();
1317 /* Allocate a new lock class and add it to the hash. */
1318 class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1321 if (!debug_locks_off_graph_unlock()) {
1325 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1330 __set_bit(class - lock_classes, lock_classes_in_use);
1331 debug_atomic_inc(nr_unused_locks);
1333 class->name = lock->name;
1334 class->subclass = subclass;
1335 WARN_ON_ONCE(!list_empty(&class->locks_before));
1336 WARN_ON_ONCE(!list_empty(&class->locks_after));
1337 class->name_version = count_matching_names(class);
1338 class->wait_type_inner = lock->wait_type_inner;
1339 class->wait_type_outer = lock->wait_type_outer;
1340 class->lock_type = lock->lock_type;
1342 * We use RCU's safe list-add method to make
1343 * parallel walking of the hash-list safe:
1345 hlist_add_head_rcu(&class->hash_entry, hash_head);
1347 * Remove the class from the free list and add it to the global list
1350 list_move_tail(&class->lock_entry, &all_lock_classes);
1351 idx = class - lock_classes;
1352 if (idx > max_lock_class_idx)
1353 max_lock_class_idx = idx;
1355 if (verbose(class)) {
1358 printk("\nnew class %px: %s", class->key, class->name);
1359 if (class->name_version > 1)
1360 printk(KERN_CONT "#%d", class->name_version);
1361 printk(KERN_CONT "\n");
1364 if (!graph_lock()) {
1371 out_set_class_cache:
1372 if (!subclass || force)
1373 lock->class_cache[0] = class;
1374 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1375 lock->class_cache[subclass] = class;
1378 * Hash collision, did we smoke some? We found a class with a matching
1379 * hash but the subclass -- which is hashed in -- didn't match.
1381 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1387 #ifdef CONFIG_PROVE_LOCKING
1389 * Allocate a lockdep entry. (assumes the graph_lock held, returns
1390 * with NULL on failure)
1392 static struct lock_list *alloc_list_entry(void)
1394 int idx = find_first_zero_bit(list_entries_in_use,
1395 ARRAY_SIZE(list_entries));
1397 if (idx >= ARRAY_SIZE(list_entries)) {
1398 if (!debug_locks_off_graph_unlock())
1401 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1406 __set_bit(idx, list_entries_in_use);
1407 return list_entries + idx;
1411 * Add a new dependency to the head of the list:
1413 static int add_lock_to_list(struct lock_class *this,
1414 struct lock_class *links_to, struct list_head *head,
1415 u16 distance, u8 dep,
1416 const struct lock_trace *trace)
1418 struct lock_list *entry;
1420 * Lock not present yet - get a new dependency struct and
1421 * add it to the list:
1423 entry = alloc_list_entry();
1427 entry->class = this;
1428 entry->links_to = links_to;
1430 entry->distance = distance;
1431 entry->trace = trace;
1433 * Both allocation and removal are done under the graph lock; but
1434 * iteration is under RCU-sched; see look_up_lock_class() and
1435 * lockdep_free_key_range().
1437 list_add_tail_rcu(&entry->entry, head);
1443 * For good efficiency of modular, we use power of 2
1445 #define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
1446 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
1449 * The circular_queue and helpers are used to implement graph
1450 * breadth-first search (BFS) algorithm, by which we can determine
1451 * whether there is a path from a lock to another. In deadlock checks,
1452 * a path from the next lock to be acquired to a previous held lock
1453 * indicates that adding the <prev> -> <next> lock dependency will
1454 * produce a circle in the graph. Breadth-first search instead of
1455 * depth-first search is used in order to find the shortest (circular)
1458 struct circular_queue {
1459 struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1460 unsigned int front, rear;
1463 static struct circular_queue lock_cq;
1465 unsigned int max_bfs_queue_depth;
1467 static unsigned int lockdep_dependency_gen_id;
1469 static inline void __cq_init(struct circular_queue *cq)
1471 cq->front = cq->rear = 0;
1472 lockdep_dependency_gen_id++;
1475 static inline int __cq_empty(struct circular_queue *cq)
1477 return (cq->front == cq->rear);
1480 static inline int __cq_full(struct circular_queue *cq)
1482 return ((cq->rear + 1) & CQ_MASK) == cq->front;
1485 static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1490 cq->element[cq->rear] = elem;
1491 cq->rear = (cq->rear + 1) & CQ_MASK;
1496 * Dequeue an element from the circular_queue, return a lock_list if
1497 * the queue is not empty, or NULL if otherwise.
1499 static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1501 struct lock_list * lock;
1506 lock = cq->element[cq->front];
1507 cq->front = (cq->front + 1) & CQ_MASK;
1512 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
1514 return (cq->rear - cq->front) & CQ_MASK;
1517 static inline void mark_lock_accessed(struct lock_list *lock)
1519 lock->class->dep_gen_id = lockdep_dependency_gen_id;
1522 static inline void visit_lock_entry(struct lock_list *lock,
1523 struct lock_list *parent)
1525 lock->parent = parent;
1528 static inline unsigned long lock_accessed(struct lock_list *lock)
1530 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1533 static inline struct lock_list *get_lock_parent(struct lock_list *child)
1535 return child->parent;
1538 static inline int get_lock_depth(struct lock_list *child)
1541 struct lock_list *parent;
1543 while ((parent = get_lock_parent(child))) {
1551 * Return the forward or backward dependency list.
1553 * @lock: the lock_list to get its class's dependency list
1554 * @offset: the offset to struct lock_class to determine whether it is
1555 * locks_after or locks_before
1557 static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1559 void *lock_class = lock->class;
1561 return lock_class + offset;
1564 * Return values of a bfs search:
1566 * BFS_E* indicates an error
1567 * BFS_R* indicates a result (match or not)
1569 * BFS_EINVALIDNODE: Find a invalid node in the graph.
1571 * BFS_EQUEUEFULL: The queue is full while doing the bfs.
1573 * BFS_RMATCH: Find the matched node in the graph, and put that node into
1576 * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
1580 BFS_EINVALIDNODE = -2,
1581 BFS_EQUEUEFULL = -1,
1587 * bfs_result < 0 means error
1589 static inline bool bfs_error(enum bfs_result res)
1595 * DEP_*_BIT in lock_list::dep
1597 * For dependency @prev -> @next:
1599 * SR: @prev is shared reader (->read != 0) and @next is recursive reader
1601 * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
1602 * SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
1603 * EN: @prev is exclusive locker and @next is non-recursive locker
1605 * Note that we define the value of DEP_*_BITs so that:
1606 * bit0 is prev->read == 0
1607 * bit1 is next->read != 2
1609 #define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
1610 #define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
1611 #define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
1612 #define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
1614 #define DEP_SR_MASK (1U << (DEP_SR_BIT))
1615 #define DEP_ER_MASK (1U << (DEP_ER_BIT))
1616 #define DEP_SN_MASK (1U << (DEP_SN_BIT))
1617 #define DEP_EN_MASK (1U << (DEP_EN_BIT))
1619 static inline unsigned int
1620 __calc_dep_bit(struct held_lock *prev, struct held_lock *next)
1622 return (prev->read == 0) + ((next->read != 2) << 1);
1625 static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
1627 return 1U << __calc_dep_bit(prev, next);
1631 * calculate the dep_bit for backwards edges. We care about whether @prev is
1632 * shared and whether @next is recursive.
1634 static inline unsigned int
1635 __calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
1637 return (next->read != 2) + ((prev->read == 0) << 1);
1640 static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
1642 return 1U << __calc_dep_bitb(prev, next);
1646 * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
1649 static inline void __bfs_init_root(struct lock_list *lock,
1650 struct lock_class *class)
1652 lock->class = class;
1653 lock->parent = NULL;
1658 * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
1659 * root for a BFS search.
1661 * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
1662 * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
1665 static inline void bfs_init_root(struct lock_list *lock,
1666 struct held_lock *hlock)
1668 __bfs_init_root(lock, hlock_class(hlock));
1669 lock->only_xr = (hlock->read == 2);
1673 * Similar to bfs_init_root() but initialize the root for backwards BFS.
1675 * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
1676 * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
1677 * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
1679 static inline void bfs_init_rootb(struct lock_list *lock,
1680 struct held_lock *hlock)
1682 __bfs_init_root(lock, hlock_class(hlock));
1683 lock->only_xr = (hlock->read != 0);
1686 static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
1688 if (!lock || !lock->parent)
1691 return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
1692 &lock->entry, struct lock_list, entry);
1696 * Breadth-First Search to find a strong path in the dependency graph.
1698 * @source_entry: the source of the path we are searching for.
1699 * @data: data used for the second parameter of @match function
1700 * @match: match function for the search
1701 * @target_entry: pointer to the target of a matched path
1702 * @offset: the offset to struct lock_class to determine whether it is
1703 * locks_after or locks_before
1705 * We may have multiple edges (considering different kinds of dependencies,
1706 * e.g. ER and SN) between two nodes in the dependency graph. But
1707 * only the strong dependency path in the graph is relevant to deadlocks. A
1708 * strong dependency path is a dependency path that doesn't have two adjacent
1709 * dependencies as -(*R)-> -(S*)->, please see:
1711 * Documentation/locking/lockdep-design.rst
1713 * for more explanation of the definition of strong dependency paths
1715 * In __bfs(), we only traverse in the strong dependency path:
1717 * In lock_list::only_xr, we record whether the previous dependency only
1718 * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
1719 * filter out any -(S*)-> in the current dependency and after that, the
1720 * ->only_xr is set according to whether we only have -(*R)-> left.
1722 static enum bfs_result __bfs(struct lock_list *source_entry,
1724 bool (*match)(struct lock_list *entry, void *data),
1725 bool (*skip)(struct lock_list *entry, void *data),
1726 struct lock_list **target_entry,
1729 struct circular_queue *cq = &lock_cq;
1730 struct lock_list *lock = NULL;
1731 struct lock_list *entry;
1732 struct list_head *head;
1733 unsigned int cq_depth;
1736 lockdep_assert_locked();
1739 __cq_enqueue(cq, source_entry);
1741 while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
1743 return BFS_EINVALIDNODE;
1746 * Step 1: check whether we already finish on this one.
1748 * If we have visited all the dependencies from this @lock to
1749 * others (iow, if we have visited all lock_list entries in
1750 * @lock->class->locks_{after,before}) we skip, otherwise go
1751 * and visit all the dependencies in the list and mark this
1754 if (lock_accessed(lock))
1757 mark_lock_accessed(lock);
1760 * Step 2: check whether prev dependency and this form a strong
1763 if (lock->parent) { /* Parent exists, check prev dependency */
1765 bool prev_only_xr = lock->parent->only_xr;
1768 * Mask out all -(S*)-> if we only have *R in previous
1769 * step, because -(*R)-> -(S*)-> don't make up a strong
1773 dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
1775 /* If nothing left, we skip */
1779 /* If there are only -(*R)-> left, set that for the next step */
1780 lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
1784 * Step 3: we haven't visited this and there is a strong
1785 * dependency path to this, so check with @match.
1786 * If @skip is provide and returns true, we skip this
1787 * lock (and any path this lock is in).
1789 if (skip && skip(lock, data))
1792 if (match(lock, data)) {
1793 *target_entry = lock;
1798 * Step 4: if not match, expand the path by adding the
1799 * forward or backwards dependencies in the search
1803 head = get_dep_list(lock, offset);
1804 list_for_each_entry_rcu(entry, head, entry) {
1805 visit_lock_entry(entry, lock);
1808 * Note we only enqueue the first of the list into the
1809 * queue, because we can always find a sibling
1810 * dependency from one (see __bfs_next()), as a result
1811 * the space of queue is saved.
1818 if (__cq_enqueue(cq, entry))
1819 return BFS_EQUEUEFULL;
1821 cq_depth = __cq_get_elem_count(cq);
1822 if (max_bfs_queue_depth < cq_depth)
1823 max_bfs_queue_depth = cq_depth;
1827 return BFS_RNOMATCH;
1830 static inline enum bfs_result
1831 __bfs_forwards(struct lock_list *src_entry,
1833 bool (*match)(struct lock_list *entry, void *data),
1834 bool (*skip)(struct lock_list *entry, void *data),
1835 struct lock_list **target_entry)
1837 return __bfs(src_entry, data, match, skip, target_entry,
1838 offsetof(struct lock_class, locks_after));
1842 static inline enum bfs_result
1843 __bfs_backwards(struct lock_list *src_entry,
1845 bool (*match)(struct lock_list *entry, void *data),
1846 bool (*skip)(struct lock_list *entry, void *data),
1847 struct lock_list **target_entry)
1849 return __bfs(src_entry, data, match, skip, target_entry,
1850 offsetof(struct lock_class, locks_before));
1854 static void print_lock_trace(const struct lock_trace *trace,
1855 unsigned int spaces)
1857 stack_trace_print(trace->entries, trace->nr_entries, spaces);
1861 * Print a dependency chain entry (this is only done when a deadlock
1862 * has been detected):
1864 static noinline void
1865 print_circular_bug_entry(struct lock_list *target, int depth)
1867 if (debug_locks_silent)
1869 printk("\n-> #%u", depth);
1870 print_lock_name(target->class);
1871 printk(KERN_CONT ":\n");
1872 print_lock_trace(target->trace, 6);
1876 print_circular_lock_scenario(struct held_lock *src,
1877 struct held_lock *tgt,
1878 struct lock_list *prt)
1880 struct lock_class *source = hlock_class(src);
1881 struct lock_class *target = hlock_class(tgt);
1882 struct lock_class *parent = prt->class;
1885 * A direct locking problem where unsafe_class lock is taken
1886 * directly by safe_class lock, then all we need to show
1887 * is the deadlock scenario, as it is obvious that the
1888 * unsafe lock is taken under the safe lock.
1890 * But if there is a chain instead, where the safe lock takes
1891 * an intermediate lock (middle_class) where this lock is
1892 * not the same as the safe lock, then the lock chain is
1893 * used to describe the problem. Otherwise we would need
1894 * to show a different CPU case for each link in the chain
1895 * from the safe_class lock to the unsafe_class lock.
1897 if (parent != source) {
1898 printk("Chain exists of:\n ");
1899 __print_lock_name(source);
1900 printk(KERN_CONT " --> ");
1901 __print_lock_name(parent);
1902 printk(KERN_CONT " --> ");
1903 __print_lock_name(target);
1904 printk(KERN_CONT "\n\n");
1907 printk(" Possible unsafe locking scenario:\n\n");
1908 printk(" CPU0 CPU1\n");
1909 printk(" ---- ----\n");
1911 __print_lock_name(target);
1912 printk(KERN_CONT ");\n");
1914 __print_lock_name(parent);
1915 printk(KERN_CONT ");\n");
1917 __print_lock_name(target);
1918 printk(KERN_CONT ");\n");
1920 __print_lock_name(source);
1921 printk(KERN_CONT ");\n");
1922 printk("\n *** DEADLOCK ***\n\n");
1926 * When a circular dependency is detected, print the
1929 static noinline void
1930 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1931 struct held_lock *check_src,
1932 struct held_lock *check_tgt)
1934 struct task_struct *curr = current;
1936 if (debug_locks_silent)
1940 pr_warn("======================================================\n");
1941 pr_warn("WARNING: possible circular locking dependency detected\n");
1942 print_kernel_ident();
1943 pr_warn("------------------------------------------------------\n");
1944 pr_warn("%s/%d is trying to acquire lock:\n",
1945 curr->comm, task_pid_nr(curr));
1946 print_lock(check_src);
1948 pr_warn("\nbut task is already holding lock:\n");
1950 print_lock(check_tgt);
1951 pr_warn("\nwhich lock already depends on the new lock.\n\n");
1952 pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1954 print_circular_bug_entry(entry, depth);
1958 * We are about to add A -> B into the dependency graph, and in __bfs() a
1959 * strong dependency path A -> .. -> B is found: hlock_class equals
1962 * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
1963 * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
1964 * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
1965 * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
1966 * dependency graph, as any strong path ..-> A -> B ->.. we can get with
1967 * having dependency A -> B, we could already get a equivalent path ..-> A ->
1968 * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant.
1970 * We need to make sure both the start and the end of A -> .. -> B is not
1971 * weaker than A -> B. For the start part, please see the comment in
1972 * check_redundant(). For the end part, we need:
1976 * a) A -> B is -(*R)-> (everything is not weaker than that)
1980 * b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
1983 static inline bool hlock_equal(struct lock_list *entry, void *data)
1985 struct held_lock *hlock = (struct held_lock *)data;
1987 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1988 (hlock->read == 2 || /* A -> B is -(*R)-> */
1989 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1993 * We are about to add B -> A into the dependency graph, and in __bfs() a
1994 * strong dependency path A -> .. -> B is found: hlock_class equals
1997 * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
1998 * dependency cycle, that means:
2002 * a) B -> A is -(E*)->
2006 * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
2008 * as then we don't have -(*R)-> -(S*)-> in the cycle.
2010 static inline bool hlock_conflict(struct lock_list *entry, void *data)
2012 struct held_lock *hlock = (struct held_lock *)data;
2014 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
2015 (hlock->read == 0 || /* B -> A is -(E*)-> */
2016 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
2019 static noinline void print_circular_bug(struct lock_list *this,
2020 struct lock_list *target,
2021 struct held_lock *check_src,
2022 struct held_lock *check_tgt)
2024 struct task_struct *curr = current;
2025 struct lock_list *parent;
2026 struct lock_list *first_parent;
2029 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2032 this->trace = save_trace();
2036 depth = get_lock_depth(target);
2038 print_circular_bug_header(target, depth, check_src, check_tgt);
2040 parent = get_lock_parent(target);
2041 first_parent = parent;
2044 print_circular_bug_entry(parent, --depth);
2045 parent = get_lock_parent(parent);
2048 printk("\nother info that might help us debug this:\n\n");
2049 print_circular_lock_scenario(check_src, check_tgt,
2052 lockdep_print_held_locks(curr);
2054 printk("\nstack backtrace:\n");
2058 static noinline void print_bfs_bug(int ret)
2060 if (!debug_locks_off_graph_unlock())
2064 * Breadth-first-search failed, graph got corrupted?
2066 WARN(1, "lockdep bfs error:%d\n", ret);
2069 static bool noop_count(struct lock_list *entry, void *data)
2071 (*(unsigned long *)data)++;
2075 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
2077 unsigned long count = 0;
2078 struct lock_list *target_entry;
2080 __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
2084 unsigned long lockdep_count_forward_deps(struct lock_class *class)
2086 unsigned long ret, flags;
2087 struct lock_list this;
2089 __bfs_init_root(&this, class);
2091 raw_local_irq_save(flags);
2093 ret = __lockdep_count_forward_deps(&this);
2095 raw_local_irq_restore(flags);
2100 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
2102 unsigned long count = 0;
2103 struct lock_list *target_entry;
2105 __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
2110 unsigned long lockdep_count_backward_deps(struct lock_class *class)
2112 unsigned long ret, flags;
2113 struct lock_list this;
2115 __bfs_init_root(&this, class);
2117 raw_local_irq_save(flags);
2119 ret = __lockdep_count_backward_deps(&this);
2121 raw_local_irq_restore(flags);
2127 * Check that the dependency graph starting at <src> can lead to
2130 static noinline enum bfs_result
2131 check_path(struct held_lock *target, struct lock_list *src_entry,
2132 bool (*match)(struct lock_list *entry, void *data),
2133 bool (*skip)(struct lock_list *entry, void *data),
2134 struct lock_list **target_entry)
2136 enum bfs_result ret;
2138 ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
2140 if (unlikely(bfs_error(ret)))
2147 * Prove that the dependency graph starting at <src> can not
2148 * lead to <target>. If it can, there is a circle when adding
2149 * <target> -> <src> dependency.
2151 * Print an error and return BFS_RMATCH if it does.
2153 static noinline enum bfs_result
2154 check_noncircular(struct held_lock *src, struct held_lock *target,
2155 struct lock_trace **const trace)
2157 enum bfs_result ret;
2158 struct lock_list *target_entry;
2159 struct lock_list src_entry;
2161 bfs_init_root(&src_entry, src);
2163 debug_atomic_inc(nr_cyclic_checks);
2165 ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
2167 if (unlikely(ret == BFS_RMATCH)) {
2170 * If save_trace fails here, the printing might
2171 * trigger a WARN but because of the !nr_entries it
2172 * should not do bad things.
2174 *trace = save_trace();
2177 print_circular_bug(&src_entry, target_entry, src, target);
2183 #ifdef CONFIG_TRACE_IRQFLAGS
2186 * Forwards and backwards subgraph searching, for the purposes of
2187 * proving that two subgraphs can be connected by a new dependency
2188 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
2190 * A irq safe->unsafe deadlock happens with the following conditions:
2192 * 1) We have a strong dependency path A -> ... -> B
2194 * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
2195 * irq can create a new dependency B -> A (consider the case that a holder
2196 * of B gets interrupted by an irq whose handler will try to acquire A).
2198 * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
2201 * For the usage bits of B:
2202 * a) if A -> B is -(*N)->, then B -> A could be any type, so any
2203 * ENABLED_IRQ usage suffices.
2204 * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
2205 * ENABLED_IRQ_*_READ usage suffices.
2207 * For the usage bits of A:
2208 * c) if A -> B is -(E*)->, then B -> A could be any type, so any
2209 * USED_IN_IRQ usage suffices.
2210 * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
2211 * USED_IN_IRQ_*_READ usage suffices.
2215 * There is a strong dependency path in the dependency graph: A -> B, and now
2216 * we need to decide which usage bit of A should be accumulated to detect
2217 * safe->unsafe bugs.
2219 * Note that usage_accumulate() is used in backwards search, so ->only_xr
2220 * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
2222 * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
2223 * path, any usage of A should be considered. Otherwise, we should only
2224 * consider _READ usage.
2226 static inline bool usage_accumulate(struct lock_list *entry, void *mask)
2228 if (!entry->only_xr)
2229 *(unsigned long *)mask |= entry->class->usage_mask;
2230 else /* Mask out _READ usage bits */
2231 *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
2237 * There is a strong dependency path in the dependency graph: A -> B, and now
2238 * we need to decide which usage bit of B conflicts with the usage bits of A,
2239 * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
2241 * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
2242 * path, any usage of B should be considered. Otherwise, we should only
2243 * consider _READ usage.
2245 static inline bool usage_match(struct lock_list *entry, void *mask)
2247 if (!entry->only_xr)
2248 return !!(entry->class->usage_mask & *(unsigned long *)mask);
2249 else /* Mask out _READ usage bits */
2250 return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
2253 static inline bool usage_skip(struct lock_list *entry, void *mask)
2256 * Skip local_lock() for irq inversion detection.
2258 * For !RT, local_lock() is not a real lock, so it won't carry any
2261 * For RT, an irq inversion happens when we have lock A and B, and on
2262 * some CPU we can have:
2268 * where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
2270 * Now we prove local_lock() cannot exist in that dependency. First we
2271 * have the observation for any lock chain L1 -> ... -> Ln, for any
2272 * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
2273 * wait context check will complain. And since B is not a sleep lock,
2274 * therefore B.inner_wait_type >= 2, and since the inner_wait_type of
2275 * local_lock() is 3, which is greater than 2, therefore there is no
2276 * way the local_lock() exists in the dependency B -> ... -> A.
2278 * As a result, we will skip local_lock(), when we search for irq
2281 if (entry->class->lock_type == LD_LOCK_PERCPU) {
2282 if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
2292 * Find a node in the forwards-direction dependency sub-graph starting
2293 * at @root->class that matches @bit.
2295 * Return BFS_MATCH if such a node exists in the subgraph, and put that node
2296 * into *@target_entry.
2298 static enum bfs_result
2299 find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
2300 struct lock_list **target_entry)
2302 enum bfs_result result;
2304 debug_atomic_inc(nr_find_usage_forwards_checks);
2306 result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2312 * Find a node in the backwards-direction dependency sub-graph starting
2313 * at @root->class that matches @bit.
2315 static enum bfs_result
2316 find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
2317 struct lock_list **target_entry)
2319 enum bfs_result result;
2321 debug_atomic_inc(nr_find_usage_backwards_checks);
2323 result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2328 static void print_lock_class_header(struct lock_class *class, int depth)
2332 printk("%*s->", depth, "");
2333 print_lock_name(class);
2334 #ifdef CONFIG_DEBUG_LOCKDEP
2335 printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
2337 printk(KERN_CONT " {\n");
2339 for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
2340 if (class->usage_mask & (1 << bit)) {
2343 len += printk("%*s %s", depth, "", usage_str[bit]);
2344 len += printk(KERN_CONT " at:\n");
2345 print_lock_trace(class->usage_traces[bit], len);
2348 printk("%*s }\n", depth, "");
2350 printk("%*s ... key at: [<%px>] %pS\n",
2351 depth, "", class->key, class->key);
2355 * Dependency path printing:
2357 * After BFS we get a lock dependency path (linked via ->parent of lock_list),
2358 * printing out each lock in the dependency path will help on understanding how
2359 * the deadlock could happen. Here are some details about dependency path
2362 * 1) A lock_list can be either forwards or backwards for a lock dependency,
2363 * for a lock dependency A -> B, there are two lock_lists:
2365 * a) lock_list in the ->locks_after list of A, whose ->class is B and
2366 * ->links_to is A. In this case, we can say the lock_list is
2367 * "A -> B" (forwards case).
2369 * b) lock_list in the ->locks_before list of B, whose ->class is A
2370 * and ->links_to is B. In this case, we can say the lock_list is
2371 * "B <- A" (bacwards case).
2373 * The ->trace of both a) and b) point to the call trace where B was
2374 * acquired with A held.
2376 * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't
2377 * represent a certain lock dependency, it only provides an initial entry
2378 * for BFS. For example, BFS may introduce a "helper" lock_list whose
2379 * ->class is A, as a result BFS will search all dependencies starting with
2380 * A, e.g. A -> B or A -> C.
2382 * The notation of a forwards helper lock_list is like "-> A", which means
2383 * we should search the forwards dependencies starting with "A", e.g A -> B
2386 * The notation of a bacwards helper lock_list is like "<- B", which means
2387 * we should search the backwards dependencies ending with "B", e.g.
2392 * printk the shortest lock dependencies from @root to @leaf in reverse order.
2394 * We have a lock dependency path as follow:
2400 * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list |
2401 * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln|
2403 * , so it's natural that we start from @leaf and print every ->class and
2404 * ->trace until we reach the @root.
2407 print_shortest_lock_dependencies(struct lock_list *leaf,
2408 struct lock_list *root)
2410 struct lock_list *entry = leaf;
2413 /*compute depth from generated tree by BFS*/
2414 depth = get_lock_depth(leaf);
2417 print_lock_class_header(entry->class, depth);
2418 printk("%*s ... acquired at:\n", depth, "");
2419 print_lock_trace(entry->trace, 2);
2422 if (depth == 0 && (entry != root)) {
2423 printk("lockdep:%s bad path found in chain graph\n", __func__);
2427 entry = get_lock_parent(entry);
2429 } while (entry && (depth >= 0));
2433 * printk the shortest lock dependencies from @leaf to @root.
2435 * We have a lock dependency path (from a backwards search) as follow:
2441 * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list |
2442 * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln |
2444 * , so when we iterate from @leaf to @root, we actually print the lock
2445 * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
2447 * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
2448 * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
2449 * trace of L1 in the dependency path, which is alright, because most of the
2450 * time we can figure out where L1 is held from the call trace of L2.
2453 print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
2454 struct lock_list *root)
2456 struct lock_list *entry = leaf;
2457 const struct lock_trace *trace = NULL;
2460 /*compute depth from generated tree by BFS*/
2461 depth = get_lock_depth(leaf);
2464 print_lock_class_header(entry->class, depth);
2466 printk("%*s ... acquired at:\n", depth, "");
2467 print_lock_trace(trace, 2);
2472 * Record the pointer to the trace for the next lock_list
2473 * entry, see the comments for the function.
2475 trace = entry->trace;
2477 if (depth == 0 && (entry != root)) {
2478 printk("lockdep:%s bad path found in chain graph\n", __func__);
2482 entry = get_lock_parent(entry);
2484 } while (entry && (depth >= 0));
2488 print_irq_lock_scenario(struct lock_list *safe_entry,
2489 struct lock_list *unsafe_entry,
2490 struct lock_class *prev_class,
2491 struct lock_class *next_class)
2493 struct lock_class *safe_class = safe_entry->class;
2494 struct lock_class *unsafe_class = unsafe_entry->class;
2495 struct lock_class *middle_class = prev_class;
2497 if (middle_class == safe_class)
2498 middle_class = next_class;
2501 * A direct locking problem where unsafe_class lock is taken
2502 * directly by safe_class lock, then all we need to show
2503 * is the deadlock scenario, as it is obvious that the
2504 * unsafe lock is taken under the safe lock.
2506 * But if there is a chain instead, where the safe lock takes
2507 * an intermediate lock (middle_class) where this lock is
2508 * not the same as the safe lock, then the lock chain is
2509 * used to describe the problem. Otherwise we would need
2510 * to show a different CPU case for each link in the chain
2511 * from the safe_class lock to the unsafe_class lock.
2513 if (middle_class != unsafe_class) {
2514 printk("Chain exists of:\n ");
2515 __print_lock_name(safe_class);
2516 printk(KERN_CONT " --> ");
2517 __print_lock_name(middle_class);
2518 printk(KERN_CONT " --> ");
2519 __print_lock_name(unsafe_class);
2520 printk(KERN_CONT "\n\n");
2523 printk(" Possible interrupt unsafe locking scenario:\n\n");
2524 printk(" CPU0 CPU1\n");
2525 printk(" ---- ----\n");
2527 __print_lock_name(unsafe_class);
2528 printk(KERN_CONT ");\n");
2529 printk(" local_irq_disable();\n");
2531 __print_lock_name(safe_class);
2532 printk(KERN_CONT ");\n");
2534 __print_lock_name(middle_class);
2535 printk(KERN_CONT ");\n");
2536 printk(" <Interrupt>\n");
2538 __print_lock_name(safe_class);
2539 printk(KERN_CONT ");\n");
2540 printk("\n *** DEADLOCK ***\n\n");
2544 print_bad_irq_dependency(struct task_struct *curr,
2545 struct lock_list *prev_root,
2546 struct lock_list *next_root,
2547 struct lock_list *backwards_entry,
2548 struct lock_list *forwards_entry,
2549 struct held_lock *prev,
2550 struct held_lock *next,
2551 enum lock_usage_bit bit1,
2552 enum lock_usage_bit bit2,
2553 const char *irqclass)
2555 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2559 pr_warn("=====================================================\n");
2560 pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2561 irqclass, irqclass);
2562 print_kernel_ident();
2563 pr_warn("-----------------------------------------------------\n");
2564 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2565 curr->comm, task_pid_nr(curr),
2566 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
2567 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2568 lockdep_hardirqs_enabled(),
2569 curr->softirqs_enabled);
2572 pr_warn("\nand this task is already holding:\n");
2574 pr_warn("which would create a new lock dependency:\n");
2575 print_lock_name(hlock_class(prev));
2577 print_lock_name(hlock_class(next));
2580 pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2582 print_lock_name(backwards_entry->class);
2583 pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2585 print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2587 pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2588 print_lock_name(forwards_entry->class);
2589 pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2592 print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2594 pr_warn("\nother info that might help us debug this:\n\n");
2595 print_irq_lock_scenario(backwards_entry, forwards_entry,
2596 hlock_class(prev), hlock_class(next));
2598 lockdep_print_held_locks(curr);
2600 pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2601 print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
2603 pr_warn("\nthe dependencies between the lock to be acquired");
2604 pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2605 next_root->trace = save_trace();
2606 if (!next_root->trace)
2608 print_shortest_lock_dependencies(forwards_entry, next_root);
2610 pr_warn("\nstack backtrace:\n");
2614 static const char *state_names[] = {
2615 #define LOCKDEP_STATE(__STATE) \
2616 __stringify(__STATE),
2617 #include "lockdep_states.h"
2618 #undef LOCKDEP_STATE
2621 static const char *state_rnames[] = {
2622 #define LOCKDEP_STATE(__STATE) \
2623 __stringify(__STATE)"-READ",
2624 #include "lockdep_states.h"
2625 #undef LOCKDEP_STATE
2628 static inline const char *state_name(enum lock_usage_bit bit)
2630 if (bit & LOCK_USAGE_READ_MASK)
2631 return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2633 return state_names[bit >> LOCK_USAGE_DIR_MASK];
2637 * The bit number is encoded like:
2639 * bit0: 0 exclusive, 1 read lock
2640 * bit1: 0 used in irq, 1 irq enabled
2643 static int exclusive_bit(int new_bit)
2645 int state = new_bit & LOCK_USAGE_STATE_MASK;
2646 int dir = new_bit & LOCK_USAGE_DIR_MASK;
2649 * keep state, bit flip the direction and strip read.
2651 return state | (dir ^ LOCK_USAGE_DIR_MASK);
2655 * Observe that when given a bitmask where each bitnr is encoded as above, a
2656 * right shift of the mask transforms the individual bitnrs as -1 and
2657 * conversely, a left shift transforms into +1 for the individual bitnrs.
2659 * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2660 * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2661 * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2663 * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2665 * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2666 * all bits set) and recompose with bitnr1 flipped.
2668 static unsigned long invert_dir_mask(unsigned long mask)
2670 unsigned long excl = 0;
2673 excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2674 excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2680 * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
2681 * usage may cause deadlock too, for example:
2685 * write_lock(l1); <irq enabled>
2691 * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
2692 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
2695 * In fact, all of the following cases may cause deadlocks:
2697 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
2698 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
2699 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
2700 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
2702 * As a result, to calculate the "exclusive mask", first we invert the
2703 * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
2704 * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
2705 * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
2707 static unsigned long exclusive_mask(unsigned long mask)
2709 unsigned long excl = invert_dir_mask(mask);
2711 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2712 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2718 * Retrieve the _possible_ original mask to which @mask is
2719 * exclusive. Ie: this is the opposite of exclusive_mask().
2720 * Note that 2 possible original bits can match an exclusive
2721 * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2722 * cleared. So both are returned for each exclusive bit.
2724 static unsigned long original_mask(unsigned long mask)
2726 unsigned long excl = invert_dir_mask(mask);
2728 /* Include read in existing usages */
2729 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2730 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2736 * Find the first pair of bit match between an original
2737 * usage mask and an exclusive usage mask.
2739 static int find_exclusive_match(unsigned long mask,
2740 unsigned long excl_mask,
2741 enum lock_usage_bit *bitp,
2742 enum lock_usage_bit *excl_bitp)
2744 int bit, excl, excl_read;
2746 for_each_set_bit(bit, &mask, LOCK_USED) {
2748 * exclusive_bit() strips the read bit, however,
2749 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
2750 * to search excl | LOCK_USAGE_READ_MASK as well.
2752 excl = exclusive_bit(bit);
2753 excl_read = excl | LOCK_USAGE_READ_MASK;
2754 if (excl_mask & lock_flag(excl)) {
2758 } else if (excl_mask & lock_flag(excl_read)) {
2760 *excl_bitp = excl_read;
2768 * Prove that the new dependency does not connect a hardirq-safe(-read)
2769 * lock with a hardirq-unsafe lock - to achieve this we search
2770 * the backwards-subgraph starting at <prev>, and the
2771 * forwards-subgraph starting at <next>:
2773 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2774 struct held_lock *next)
2776 unsigned long usage_mask = 0, forward_mask, backward_mask;
2777 enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2778 struct lock_list *target_entry1;
2779 struct lock_list *target_entry;
2780 struct lock_list this, that;
2781 enum bfs_result ret;
2784 * Step 1: gather all hard/soft IRQs usages backward in an
2785 * accumulated usage mask.
2787 bfs_init_rootb(&this, prev);
2789 ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
2790 if (bfs_error(ret)) {
2795 usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2800 * Step 2: find exclusive uses forward that match the previous
2801 * backward accumulated mask.
2803 forward_mask = exclusive_mask(usage_mask);
2805 bfs_init_root(&that, next);
2807 ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2808 if (bfs_error(ret)) {
2812 if (ret == BFS_RNOMATCH)
2816 * Step 3: we found a bad match! Now retrieve a lock from the backward
2817 * list whose usage mask matches the exclusive usage mask from the
2818 * lock found on the forward list.
2820 * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
2823 * When trying to add A -> B to the graph, we find that there is a
2824 * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
2825 * that B -> ... -> M. However M is **softirq-safe**, if we use exact
2826 * invert bits of M's usage_mask, we will find another lock N that is
2827 * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
2828 * cause a inversion deadlock.
2830 backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
2832 ret = find_usage_backwards(&this, backward_mask, &target_entry);
2833 if (bfs_error(ret)) {
2837 if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
2841 * Step 4: narrow down to a pair of incompatible usage bits
2844 ret = find_exclusive_match(target_entry->class->usage_mask,
2845 target_entry1->class->usage_mask,
2846 &backward_bit, &forward_bit);
2847 if (DEBUG_LOCKS_WARN_ON(ret == -1))
2850 print_bad_irq_dependency(curr, &this, &that,
2851 target_entry, target_entry1,
2853 backward_bit, forward_bit,
2854 state_name(backward_bit));
2861 static inline int check_irq_usage(struct task_struct *curr,
2862 struct held_lock *prev, struct held_lock *next)
2867 static inline bool usage_skip(struct lock_list *entry, void *mask)
2872 #endif /* CONFIG_TRACE_IRQFLAGS */
2874 #ifdef CONFIG_LOCKDEP_SMALL
2876 * Check that the dependency graph starting at <src> can lead to
2877 * <target> or not. If it can, <src> -> <target> dependency is already
2880 * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if
2881 * any error appears in the bfs search.
2883 static noinline enum bfs_result
2884 check_redundant(struct held_lock *src, struct held_lock *target)
2886 enum bfs_result ret;
2887 struct lock_list *target_entry;
2888 struct lock_list src_entry;
2890 bfs_init_root(&src_entry, src);
2892 * Special setup for check_redundant().
2894 * To report redundant, we need to find a strong dependency path that
2895 * is equal to or stronger than <src> -> <target>. So if <src> is E,
2896 * we need to let __bfs() only search for a path starting at a -(E*)->,
2897 * we achieve this by setting the initial node's ->only_xr to true in
2898 * that case. And if <prev> is S, we set initial ->only_xr to false
2899 * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
2901 src_entry.only_xr = src->read == 0;
2903 debug_atomic_inc(nr_redundant_checks);
2906 * Note: we skip local_lock() for redundant check, because as the
2907 * comment in usage_skip(), A -> local_lock() -> B and A -> B are not
2910 ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
2912 if (ret == BFS_RMATCH)
2913 debug_atomic_inc(nr_redundant);
2920 static inline enum bfs_result
2921 check_redundant(struct held_lock *src, struct held_lock *target)
2923 return BFS_RNOMATCH;
2928 static void inc_chains(int irq_context)
2930 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2931 nr_hardirq_chains++;
2932 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2933 nr_softirq_chains++;
2935 nr_process_chains++;
2938 static void dec_chains(int irq_context)
2940 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2941 nr_hardirq_chains--;
2942 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2943 nr_softirq_chains--;
2945 nr_process_chains--;
2949 print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2951 struct lock_class *next = hlock_class(nxt);
2952 struct lock_class *prev = hlock_class(prv);
2954 printk(" Possible unsafe locking scenario:\n\n");
2958 __print_lock_name(prev);
2959 printk(KERN_CONT ");\n");
2961 __print_lock_name(next);
2962 printk(KERN_CONT ");\n");
2963 printk("\n *** DEADLOCK ***\n\n");
2964 printk(" May be due to missing lock nesting notation\n\n");
2968 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
2969 struct held_lock *next)
2971 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2975 pr_warn("============================================\n");
2976 pr_warn("WARNING: possible recursive locking detected\n");
2977 print_kernel_ident();
2978 pr_warn("--------------------------------------------\n");
2979 pr_warn("%s/%d is trying to acquire lock:\n",
2980 curr->comm, task_pid_nr(curr));
2982 pr_warn("\nbut task is already holding lock:\n");
2985 pr_warn("\nother info that might help us debug this:\n");
2986 print_deadlock_scenario(next, prev);
2987 lockdep_print_held_locks(curr);
2989 pr_warn("\nstack backtrace:\n");
2994 * Check whether we are holding such a class already.
2996 * (Note that this has to be done separately, because the graph cannot
2997 * detect such classes of deadlocks.)
2999 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
3000 * lock class is held but nest_lock is also held, i.e. we rely on the
3001 * nest_lock to avoid the deadlock.
3004 check_deadlock(struct task_struct *curr, struct held_lock *next)
3006 struct held_lock *prev;
3007 struct held_lock *nest = NULL;
3010 for (i = 0; i < curr->lockdep_depth; i++) {
3011 prev = curr->held_locks + i;
3013 if (prev->instance == next->nest_lock)
3016 if (hlock_class(prev) != hlock_class(next))
3020 * Allow read-after-read recursion of the same
3021 * lock class (i.e. read_lock(lock)+read_lock(lock)):
3023 if ((next->read == 2) && prev->read)
3027 * We're holding the nest_lock, which serializes this lock's
3028 * nesting behaviour.
3033 print_deadlock_bug(curr, prev, next);
3040 * There was a chain-cache miss, and we are about to add a new dependency
3041 * to a previous lock. We validate the following rules:
3043 * - would the adding of the <prev> -> <next> dependency create a
3044 * circular dependency in the graph? [== circular deadlock]
3046 * - does the new prev->next dependency connect any hardirq-safe lock
3047 * (in the full backwards-subgraph starting at <prev>) with any
3048 * hardirq-unsafe lock (in the full forwards-subgraph starting at
3049 * <next>)? [== illegal lock inversion with hardirq contexts]
3051 * - does the new prev->next dependency connect any softirq-safe lock
3052 * (in the full backwards-subgraph starting at <prev>) with any
3053 * softirq-unsafe lock (in the full forwards-subgraph starting at
3054 * <next>)? [== illegal lock inversion with softirq contexts]
3056 * any of these scenarios could lead to a deadlock.
3058 * Then if all the validations pass, we add the forwards and backwards
3062 check_prev_add(struct task_struct *curr, struct held_lock *prev,
3063 struct held_lock *next, u16 distance,
3064 struct lock_trace **const trace)
3066 struct lock_list *entry;
3067 enum bfs_result ret;
3069 if (!hlock_class(prev)->key || !hlock_class(next)->key) {
3071 * The warning statements below may trigger a use-after-free
3072 * of the class name. It is better to trigger a use-after free
3073 * and to have the class name most of the time instead of not
3074 * having the class name available.
3076 WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
3077 "Detected use-after-free of lock class %px/%s\n",
3079 hlock_class(prev)->name);
3080 WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
3081 "Detected use-after-free of lock class %px/%s\n",
3083 hlock_class(next)->name);
3088 * Prove that the new <prev> -> <next> dependency would not
3089 * create a circular dependency in the graph. (We do this by
3090 * a breadth-first search into the graph starting at <next>,
3091 * and check whether we can reach <prev>.)
3093 * The search is limited by the size of the circular queue (i.e.,
3094 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
3095 * in the graph whose neighbours are to be checked.
3097 ret = check_noncircular(next, prev, trace);
3098 if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
3101 if (!check_irq_usage(curr, prev, next))
3105 * Is the <prev> -> <next> dependency already present?
3107 * (this may occur even though this is a new chain: consider
3108 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
3109 * chains - the second one will be new, but L1 already has
3110 * L2 added to its dependency list, due to the first chain.)
3112 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
3113 if (entry->class == hlock_class(next)) {
3115 entry->distance = 1;
3116 entry->dep |= calc_dep(prev, next);
3119 * Also, update the reverse dependency in @next's
3120 * ->locks_before list.
3122 * Here we reuse @entry as the cursor, which is fine
3123 * because we won't go to the next iteration of the
3126 * For normal cases, we return in the inner loop.
3128 * If we fail to return, we have inconsistency, i.e.
3129 * <prev>::locks_after contains <next> while
3130 * <next>::locks_before doesn't contain <prev>. In
3131 * that case, we return after the inner and indicate
3132 * something is wrong.
3134 list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
3135 if (entry->class == hlock_class(prev)) {
3137 entry->distance = 1;
3138 entry->dep |= calc_depb(prev, next);
3143 /* <prev> is not found in <next>::locks_before */
3149 * Is the <prev> -> <next> link redundant?
3151 ret = check_redundant(prev, next);
3154 else if (ret == BFS_RMATCH)
3158 *trace = save_trace();
3164 * Ok, all validations passed, add the new lock
3165 * to the previous lock's dependency list:
3167 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
3168 &hlock_class(prev)->locks_after, distance,
3169 calc_dep(prev, next), *trace);
3174 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
3175 &hlock_class(next)->locks_before, distance,
3176 calc_depb(prev, next), *trace);
3184 * Add the dependency to all directly-previous locks that are 'relevant'.
3185 * The ones that are relevant are (in increasing distance from curr):
3186 * all consecutive trylock entries and the final non-trylock entry - or
3187 * the end of this context's lock-chain - whichever comes first.
3190 check_prevs_add(struct task_struct *curr, struct held_lock *next)
3192 struct lock_trace *trace = NULL;
3193 int depth = curr->lockdep_depth;
3194 struct held_lock *hlock;
3199 * Depth must not be zero for a non-head lock:
3204 * At least two relevant locks must exist for this
3207 if (curr->held_locks[depth].irq_context !=
3208 curr->held_locks[depth-1].irq_context)
3212 u16 distance = curr->lockdep_depth - depth + 1;
3213 hlock = curr->held_locks + depth - 1;
3216 int ret = check_prev_add(curr, hlock, next, distance, &trace);
3221 * Stop after the first non-trylock entry,
3222 * as non-trylock entries have added their
3223 * own direct dependencies already, so this
3224 * lock is connected to them indirectly:
3226 if (!hlock->trylock)
3232 * End of lock-stack?
3237 * Stop the search if we cross into another context:
3239 if (curr->held_locks[depth].irq_context !=
3240 curr->held_locks[depth-1].irq_context)
3245 if (!debug_locks_off_graph_unlock())
3249 * Clearly we all shouldn't be here, but since we made it we
3250 * can reliable say we messed up our state. See the above two
3251 * gotos for reasons why we could possibly end up here.
3258 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
3259 static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
3260 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
3261 unsigned long nr_zapped_lock_chains;
3262 unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
3263 unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
3264 unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
3267 * The first 2 chain_hlocks entries in the chain block in the bucket
3268 * list contains the following meta data:
3271 * Bit 15 - always set to 1 (it is not a class index)
3272 * Bits 0-14 - upper 15 bits of the next block index
3273 * entry[1] - lower 16 bits of next block index
3275 * A next block index of all 1 bits means it is the end of the list.
3277 * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
3278 * the chain block size:
3280 * entry[2] - upper 16 bits of the chain block size
3281 * entry[3] - lower 16 bits of the chain block size
3283 #define MAX_CHAIN_BUCKETS 16
3284 #define CHAIN_BLK_FLAG (1U << 15)
3285 #define CHAIN_BLK_LIST_END 0xFFFFU
3287 static int chain_block_buckets[MAX_CHAIN_BUCKETS];
3289 static inline int size_to_bucket(int size)
3291 if (size > MAX_CHAIN_BUCKETS)
3298 * Iterate all the chain blocks in a bucket.
3300 #define for_each_chain_block(bucket, prev, curr) \
3301 for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
3303 (prev) = (curr), (curr) = chain_block_next(curr))
3308 static inline int chain_block_next(int offset)
3310 int next = chain_hlocks[offset];
3312 WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
3314 if (next == CHAIN_BLK_LIST_END)
3317 next &= ~CHAIN_BLK_FLAG;
3319 next |= chain_hlocks[offset + 1];
3327 static inline int chain_block_size(int offset)
3329 return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
3332 static inline void init_chain_block(int offset, int next, int bucket, int size)
3334 chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
3335 chain_hlocks[offset + 1] = (u16)next;
3337 if (size && !bucket) {
3338 chain_hlocks[offset + 2] = size >> 16;
3339 chain_hlocks[offset + 3] = (u16)size;
3343 static inline void add_chain_block(int offset, int size)
3345 int bucket = size_to_bucket(size);
3346 int next = chain_block_buckets[bucket];
3349 if (unlikely(size < 2)) {
3351 * We can't store single entries on the freelist. Leak them.
3353 * One possible way out would be to uniquely mark them, other
3354 * than with CHAIN_BLK_FLAG, such that we can recover them when
3355 * the block before it is re-added.
3358 nr_lost_chain_hlocks++;
3362 nr_free_chain_hlocks += size;
3364 nr_large_chain_blocks++;
3367 * Variable sized, sort large to small.
3369 for_each_chain_block(0, prev, curr) {
3370 if (size >= chain_block_size(curr))
3373 init_chain_block(offset, curr, 0, size);
3375 chain_block_buckets[0] = offset;
3377 init_chain_block(prev, offset, 0, 0);
3381 * Fixed size, add to head.
3383 init_chain_block(offset, next, bucket, size);
3384 chain_block_buckets[bucket] = offset;
3388 * Only the first block in the list can be deleted.
3390 * For the variable size bucket[0], the first block (the largest one) is
3391 * returned, broken up and put back into the pool. So if a chain block of
3392 * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
3393 * queued up after the primordial chain block and never be used until the
3394 * hlock entries in the primordial chain block is almost used up. That
3395 * causes fragmentation and reduce allocation efficiency. That can be
3396 * monitored by looking at the "large chain blocks" number in lockdep_stats.
3398 static inline void del_chain_block(int bucket, int size, int next)
3400 nr_free_chain_hlocks -= size;
3401 chain_block_buckets[bucket] = next;
3404 nr_large_chain_blocks--;
3407 static void init_chain_block_buckets(void)
3411 for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
3412 chain_block_buckets[i] = -1;
3414 add_chain_block(0, ARRAY_SIZE(chain_hlocks));
3418 * Return offset of a chain block of the right size or -1 if not found.
3420 * Fairly simple worst-fit allocator with the addition of a number of size
3421 * specific free lists.
3423 static int alloc_chain_hlocks(int req)
3425 int bucket, curr, size;
3428 * We rely on the MSB to act as an escape bit to denote freelist
3429 * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
3431 BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
3433 init_data_structures_once();
3435 if (nr_free_chain_hlocks < req)
3439 * We require a minimum of 2 (u16) entries to encode a freelist
3443 bucket = size_to_bucket(req);
3444 curr = chain_block_buckets[bucket];
3448 del_chain_block(bucket, req, chain_block_next(curr));
3452 curr = chain_block_buckets[0];
3456 * The variable sized freelist is sorted by size; the first entry is
3457 * the largest. Use it if it fits.
3460 size = chain_block_size(curr);
3461 if (likely(size >= req)) {
3462 del_chain_block(0, size, chain_block_next(curr));
3463 add_chain_block(curr + req, size - req);
3469 * Last resort, split a block in a larger sized bucket.
3471 for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
3472 bucket = size_to_bucket(size);
3473 curr = chain_block_buckets[bucket];
3477 del_chain_block(bucket, size, chain_block_next(curr));
3478 add_chain_block(curr + req, size - req);
3485 static inline void free_chain_hlocks(int base, int size)
3487 add_chain_block(base, max(size, 2));
3490 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
3492 u16 chain_hlock = chain_hlocks[chain->base + i];
3493 unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
3495 return lock_classes + class_idx;
3499 * Returns the index of the first held_lock of the current chain
3501 static inline int get_first_held_lock(struct task_struct *curr,
3502 struct held_lock *hlock)
3505 struct held_lock *hlock_curr;
3507 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
3508 hlock_curr = curr->held_locks + i;
3509 if (hlock_curr->irq_context != hlock->irq_context)
3517 #ifdef CONFIG_DEBUG_LOCKDEP
3519 * Returns the next chain_key iteration
3521 static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
3523 u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
3525 printk(" hlock_id:%d -> chain_key:%016Lx",
3526 (unsigned int)hlock_id,
3527 (unsigned long long)new_chain_key);
3528 return new_chain_key;
3532 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
3534 struct held_lock *hlock;
3535 u64 chain_key = INITIAL_CHAIN_KEY;
3536 int depth = curr->lockdep_depth;
3537 int i = get_first_held_lock(curr, hlock_next);
3539 printk("depth: %u (irq_context %u)\n", depth - i + 1,
3540 hlock_next->irq_context);
3541 for (; i < depth; i++) {
3542 hlock = curr->held_locks + i;
3543 chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
3548 print_chain_key_iteration(hlock_id(hlock_next), chain_key);
3549 print_lock(hlock_next);
3552 static void print_chain_keys_chain(struct lock_chain *chain)
3555 u64 chain_key = INITIAL_CHAIN_KEY;
3558 printk("depth: %u\n", chain->depth);
3559 for (i = 0; i < chain->depth; i++) {
3560 hlock_id = chain_hlocks[chain->base + i];
3561 chain_key = print_chain_key_iteration(hlock_id, chain_key);
3563 print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
3568 static void print_collision(struct task_struct *curr,
3569 struct held_lock *hlock_next,
3570 struct lock_chain *chain)
3573 pr_warn("============================\n");
3574 pr_warn("WARNING: chain_key collision\n");
3575 print_kernel_ident();
3576 pr_warn("----------------------------\n");
3577 pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
3578 pr_warn("Hash chain already cached but the contents don't match!\n");
3580 pr_warn("Held locks:");
3581 print_chain_keys_held_locks(curr, hlock_next);
3583 pr_warn("Locks in cached chain:");
3584 print_chain_keys_chain(chain);
3586 pr_warn("\nstack backtrace:\n");
3592 * Checks whether the chain and the current held locks are consistent
3593 * in depth and also in content. If they are not it most likely means
3594 * that there was a collision during the calculation of the chain_key.
3595 * Returns: 0 not passed, 1 passed
3597 static int check_no_collision(struct task_struct *curr,
3598 struct held_lock *hlock,
3599 struct lock_chain *chain)
3601 #ifdef CONFIG_DEBUG_LOCKDEP
3604 i = get_first_held_lock(curr, hlock);
3606 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
3607 print_collision(curr, hlock, chain);
3611 for (j = 0; j < chain->depth - 1; j++, i++) {
3612 id = hlock_id(&curr->held_locks[i]);
3614 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
3615 print_collision(curr, hlock, chain);
3624 * Given an index that is >= -1, return the index of the next lock chain.
3625 * Return -2 if there is no next lock chain.
3627 long lockdep_next_lockchain(long i)
3629 i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
3630 return i < ARRAY_SIZE(lock_chains) ? i : -2;
3633 unsigned long lock_chain_count(void)
3635 return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
3638 /* Must be called with the graph lock held. */
3639 static struct lock_chain *alloc_lock_chain(void)
3641 int idx = find_first_zero_bit(lock_chains_in_use,
3642 ARRAY_SIZE(lock_chains));
3644 if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
3646 __set_bit(idx, lock_chains_in_use);
3647 return lock_chains + idx;
3651 * Adds a dependency chain into chain hashtable. And must be called with
3654 * Return 0 if fail, and graph_lock is released.
3655 * Return 1 if succeed, with graph_lock held.
3657 static inline int add_chain_cache(struct task_struct *curr,
3658 struct held_lock *hlock,
3661 struct hlist_head *hash_head = chainhashentry(chain_key);
3662 struct lock_chain *chain;
3666 * The caller must hold the graph lock, ensure we've got IRQs
3667 * disabled to make this an IRQ-safe lock.. for recursion reasons
3668 * lockdep won't complain about its own locking errors.
3670 if (lockdep_assert_locked())
3673 chain = alloc_lock_chain();
3675 if (!debug_locks_off_graph_unlock())
3678 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
3682 chain->chain_key = chain_key;
3683 chain->irq_context = hlock->irq_context;
3684 i = get_first_held_lock(curr, hlock);
3685 chain->depth = curr->lockdep_depth + 1 - i;
3687 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
3688 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
3689 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
3691 j = alloc_chain_hlocks(chain->depth);
3693 if (!debug_locks_off_graph_unlock())
3696 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
3702 for (j = 0; j < chain->depth - 1; j++, i++) {
3703 int lock_id = hlock_id(curr->held_locks + i);
3705 chain_hlocks[chain->base + j] = lock_id;
3707 chain_hlocks[chain->base + j] = hlock_id(hlock);
3708 hlist_add_head_rcu(&chain->entry, hash_head);
3709 debug_atomic_inc(chain_lookup_misses);
3710 inc_chains(chain->irq_context);
3716 * Look up a dependency chain. Must be called with either the graph lock or
3717 * the RCU read lock held.
3719 static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
3721 struct hlist_head *hash_head = chainhashentry(chain_key);
3722 struct lock_chain *chain;
3724 hlist_for_each_entry_rcu(chain, hash_head, entry) {
3725 if (READ_ONCE(chain->chain_key) == chain_key) {
3726 debug_atomic_inc(chain_lookup_hits);
3734 * If the key is not present yet in dependency chain cache then
3735 * add it and return 1 - in this case the new dependency chain is
3736 * validated. If the key is already hashed, return 0.
3737 * (On return with 1 graph_lock is held.)
3739 static inline int lookup_chain_cache_add(struct task_struct *curr,
3740 struct held_lock *hlock,
3743 struct lock_class *class = hlock_class(hlock);
3744 struct lock_chain *chain = lookup_chain_cache(chain_key);
3748 if (!check_no_collision(curr, hlock, chain))
3751 if (very_verbose(class)) {
3752 printk("\nhash chain already cached, key: "
3753 "%016Lx tail class: [%px] %s\n",
3754 (unsigned long long)chain_key,
3755 class->key, class->name);
3761 if (very_verbose(class)) {
3762 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
3763 (unsigned long long)chain_key, class->key, class->name);
3770 * We have to walk the chain again locked - to avoid duplicates:
3772 chain = lookup_chain_cache(chain_key);
3778 if (!add_chain_cache(curr, hlock, chain_key))
3784 static int validate_chain(struct task_struct *curr,
3785 struct held_lock *hlock,
3786 int chain_head, u64 chain_key)
3789 * Trylock needs to maintain the stack of held locks, but it
3790 * does not add new dependencies, because trylock can be done
3793 * We look up the chain_key and do the O(N^2) check and update of
3794 * the dependencies only if this is a new dependency chain.
3795 * (If lookup_chain_cache_add() return with 1 it acquires
3796 * graph_lock for us)
3798 if (!hlock->trylock && hlock->check &&
3799 lookup_chain_cache_add(curr, hlock, chain_key)) {
3801 * Check whether last held lock:
3803 * - is irq-safe, if this lock is irq-unsafe
3804 * - is softirq-safe, if this lock is hardirq-unsafe
3806 * And check whether the new lock's dependency graph
3807 * could lead back to the previous lock:
3809 * - within the current held-lock stack
3810 * - across our accumulated lock dependency records
3812 * any of these scenarios could lead to a deadlock.
3815 * The simple case: does the current hold the same lock
3818 int ret = check_deadlock(curr, hlock);
3823 * Add dependency only if this lock is not the head
3824 * of the chain, and if the new lock introduces no more
3825 * lock dependency (because we already hold a lock with the
3826 * same lock class) nor deadlock (because the nest_lock
3827 * serializes nesting locks), see the comments for
3830 if (!chain_head && ret != 2) {
3831 if (!check_prevs_add(curr, hlock))
3837 /* after lookup_chain_cache_add(): */
3838 if (unlikely(!debug_locks))
3845 static inline int validate_chain(struct task_struct *curr,
3846 struct held_lock *hlock,
3847 int chain_head, u64 chain_key)
3852 static void init_chain_block_buckets(void) { }
3853 #endif /* CONFIG_PROVE_LOCKING */
3856 * We are building curr_chain_key incrementally, so double-check
3857 * it from scratch, to make sure that it's done correctly:
3859 static void check_chain_key(struct task_struct *curr)
3861 #ifdef CONFIG_DEBUG_LOCKDEP
3862 struct held_lock *hlock, *prev_hlock = NULL;
3864 u64 chain_key = INITIAL_CHAIN_KEY;
3866 for (i = 0; i < curr->lockdep_depth; i++) {
3867 hlock = curr->held_locks + i;
3868 if (chain_key != hlock->prev_chain_key) {
3871 * We got mighty confused, our chain keys don't match
3872 * with what we expect, someone trample on our task state?
3874 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3875 curr->lockdep_depth, i,
3876 (unsigned long long)chain_key,
3877 (unsigned long long)hlock->prev_chain_key);
3882 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3883 * it registered lock class index?
3885 if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3888 if (prev_hlock && (prev_hlock->irq_context !=
3889 hlock->irq_context))
3890 chain_key = INITIAL_CHAIN_KEY;
3891 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
3894 if (chain_key != curr->curr_chain_key) {
3897 * More smoking hash instead of calculating it, damn see these
3898 * numbers float.. I bet that a pink elephant stepped on my memory.
3900 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3901 curr->lockdep_depth, i,
3902 (unsigned long long)chain_key,
3903 (unsigned long long)curr->curr_chain_key);
3908 #ifdef CONFIG_PROVE_LOCKING
3909 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3910 enum lock_usage_bit new_bit);
3912 static void print_usage_bug_scenario(struct held_lock *lock)
3914 struct lock_class *class = hlock_class(lock);
3916 printk(" Possible unsafe locking scenario:\n\n");
3920 __print_lock_name(class);
3921 printk(KERN_CONT ");\n");
3922 printk(" <Interrupt>\n");
3924 __print_lock_name(class);
3925 printk(KERN_CONT ");\n");
3926 printk("\n *** DEADLOCK ***\n\n");
3930 print_usage_bug(struct task_struct *curr, struct held_lock *this,
3931 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
3933 if (!debug_locks_off() || debug_locks_silent)
3937 pr_warn("================================\n");
3938 pr_warn("WARNING: inconsistent lock state\n");
3939 print_kernel_ident();
3940 pr_warn("--------------------------------\n");
3942 pr_warn("inconsistent {%s} -> {%s} usage.\n",
3943 usage_str[prev_bit], usage_str[new_bit]);
3945 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
3946 curr->comm, task_pid_nr(curr),
3947 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
3948 lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
3949 lockdep_hardirqs_enabled(),
3950 lockdep_softirqs_enabled(curr));
3953 pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
3954 print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
3956 print_irqtrace_events(curr);
3957 pr_warn("\nother info that might help us debug this:\n");
3958 print_usage_bug_scenario(this);
3960 lockdep_print_held_locks(curr);
3962 pr_warn("\nstack backtrace:\n");
3967 * Print out an error if an invalid bit is set:
3970 valid_state(struct task_struct *curr, struct held_lock *this,
3971 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
3973 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
3975 print_usage_bug(curr, this, bad_bit, new_bit);
3983 * print irq inversion bug:
3986 print_irq_inversion_bug(struct task_struct *curr,
3987 struct lock_list *root, struct lock_list *other,
3988 struct held_lock *this, int forwards,
3989 const char *irqclass)
3991 struct lock_list *entry = other;
3992 struct lock_list *middle = NULL;
3995 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3999 pr_warn("========================================================\n");
4000 pr_warn("WARNING: possible irq lock inversion dependency detected\n");
4001 print_kernel_ident();
4002 pr_warn("--------------------------------------------------------\n");
4003 pr_warn("%s/%d just changed the state of lock:\n",
4004 curr->comm, task_pid_nr(curr));
4007 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
4009 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
4010 print_lock_name(other->class);
4011 pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
4013 pr_warn("\nother info that might help us debug this:\n");
4015 /* Find a middle lock (if one exists) */
4016 depth = get_lock_depth(other);
4018 if (depth == 0 && (entry != root)) {
4019 pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
4023 entry = get_lock_parent(entry);
4025 } while (entry && entry != root && (depth >= 0));
4027 print_irq_lock_scenario(root, other,
4028 middle ? middle->class : root->class, other->class);
4030 print_irq_lock_scenario(other, root,
4031 middle ? middle->class : other->class, root->class);
4033 lockdep_print_held_locks(curr);
4035 pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
4036 root->trace = save_trace();
4039 print_shortest_lock_dependencies(other, root);
4041 pr_warn("\nstack backtrace:\n");
4046 * Prove that in the forwards-direction subgraph starting at <this>
4047 * there is no lock matching <mask>:
4050 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
4051 enum lock_usage_bit bit)
4053 enum bfs_result ret;
4054 struct lock_list root;
4055 struct lock_list *target_entry;
4056 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4057 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4059 bfs_init_root(&root, this);
4060 ret = find_usage_forwards(&root, usage_mask, &target_entry);
4061 if (bfs_error(ret)) {
4065 if (ret == BFS_RNOMATCH)
4068 /* Check whether write or read usage is the match */
4069 if (target_entry->class->usage_mask & lock_flag(bit)) {
4070 print_irq_inversion_bug(curr, &root, target_entry,
4071 this, 1, state_name(bit));
4073 print_irq_inversion_bug(curr, &root, target_entry,
4074 this, 1, state_name(read_bit));
4081 * Prove that in the backwards-direction subgraph starting at <this>
4082 * there is no lock matching <mask>:
4085 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
4086 enum lock_usage_bit bit)
4088 enum bfs_result ret;
4089 struct lock_list root;
4090 struct lock_list *target_entry;
4091 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4092 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4094 bfs_init_rootb(&root, this);
4095 ret = find_usage_backwards(&root, usage_mask, &target_entry);
4096 if (bfs_error(ret)) {
4100 if (ret == BFS_RNOMATCH)
4103 /* Check whether write or read usage is the match */
4104 if (target_entry->class->usage_mask & lock_flag(bit)) {
4105 print_irq_inversion_bug(curr, &root, target_entry,
4106 this, 0, state_name(bit));
4108 print_irq_inversion_bug(curr, &root, target_entry,
4109 this, 0, state_name(read_bit));
4115 void print_irqtrace_events(struct task_struct *curr)
4117 const struct irqtrace_events *trace = &curr->irqtrace;
4119 printk("irq event stamp: %u\n", trace->irq_events);
4120 printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
4121 trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
4122 (void *)trace->hardirq_enable_ip);
4123 printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
4124 trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
4125 (void *)trace->hardirq_disable_ip);
4126 printk("softirqs last enabled at (%u): [<%px>] %pS\n",
4127 trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
4128 (void *)trace->softirq_enable_ip);
4129 printk("softirqs last disabled at (%u): [<%px>] %pS\n",
4130 trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
4131 (void *)trace->softirq_disable_ip);
4134 static int HARDIRQ_verbose(struct lock_class *class)
4137 return class_filter(class);
4142 static int SOFTIRQ_verbose(struct lock_class *class)
4145 return class_filter(class);
4150 static int (*state_verbose_f[])(struct lock_class *class) = {
4151 #define LOCKDEP_STATE(__STATE) \
4153 #include "lockdep_states.h"
4154 #undef LOCKDEP_STATE
4157 static inline int state_verbose(enum lock_usage_bit bit,
4158 struct lock_class *class)
4160 return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
4163 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
4164 enum lock_usage_bit bit, const char *name);
4167 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
4168 enum lock_usage_bit new_bit)
4170 int excl_bit = exclusive_bit(new_bit);
4171 int read = new_bit & LOCK_USAGE_READ_MASK;
4172 int dir = new_bit & LOCK_USAGE_DIR_MASK;
4175 * Validate that this particular lock does not have conflicting
4178 if (!valid_state(curr, this, new_bit, excl_bit))
4182 * Check for read in write conflicts
4184 if (!read && !valid_state(curr, this, new_bit,
4185 excl_bit + LOCK_USAGE_READ_MASK))
4190 * Validate that the lock dependencies don't have conflicting usage
4195 * mark ENABLED has to look backwards -- to ensure no dependee
4196 * has USED_IN state, which, again, would allow recursion deadlocks.
4198 if (!check_usage_backwards(curr, this, excl_bit))
4202 * mark USED_IN has to look forwards -- to ensure no dependency
4203 * has ENABLED state, which would allow recursion deadlocks.
4205 if (!check_usage_forwards(curr, this, excl_bit))
4209 if (state_verbose(new_bit, hlock_class(this)))
4216 * Mark all held locks with a usage bit:
4219 mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
4221 struct held_lock *hlock;
4224 for (i = 0; i < curr->lockdep_depth; i++) {
4225 enum lock_usage_bit hlock_bit = base_bit;
4226 hlock = curr->held_locks + i;
4229 hlock_bit += LOCK_USAGE_READ_MASK;
4231 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
4236 if (!mark_lock(curr, hlock, hlock_bit))
4244 * Hardirqs will be enabled:
4246 static void __trace_hardirqs_on_caller(void)
4248 struct task_struct *curr = current;
4251 * We are going to turn hardirqs on, so set the
4252 * usage bit for all held locks:
4254 if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
4257 * If we have softirqs enabled, then set the usage
4258 * bit for all held locks. (disabled hardirqs prevented
4259 * this bit from being set before)
4261 if (curr->softirqs_enabled)
4262 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
4266 * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
4268 * Invoked before a possible transition to RCU idle from exit to user or
4269 * guest mode. This ensures that all RCU operations are done before RCU
4270 * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
4271 * invoked to set the final state.
4273 void lockdep_hardirqs_on_prepare(void)
4275 if (unlikely(!debug_locks))
4279 * NMIs do not (and cannot) track lock dependencies, nothing to do.
4281 if (unlikely(in_nmi()))
4284 if (unlikely(this_cpu_read(lockdep_recursion)))
4287 if (unlikely(lockdep_hardirqs_enabled())) {
4289 * Neither irq nor preemption are disabled here
4290 * so this is racy by nature but losing one hit
4291 * in a stat is not a big deal.
4293 __debug_atomic_inc(redundant_hardirqs_on);
4298 * We're enabling irqs and according to our state above irqs weren't
4299 * already enabled, yet we find the hardware thinks they are in fact
4300 * enabled.. someone messed up their IRQ state tracing.
4302 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4306 * See the fine text that goes along with this variable definition.
4308 if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
4312 * Can't allow enabling interrupts while in an interrupt handler,
4313 * that's general bad form and such. Recursion, limited stack etc..
4315 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
4318 current->hardirq_chain_key = current->curr_chain_key;
4320 lockdep_recursion_inc();
4321 __trace_hardirqs_on_caller();
4322 lockdep_recursion_finish();
4324 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
4326 void noinstr lockdep_hardirqs_on(unsigned long ip)
4328 struct irqtrace_events *trace = ¤t->irqtrace;
4330 if (unlikely(!debug_locks))
4334 * NMIs can happen in the middle of local_irq_{en,dis}able() where the
4335 * tracking state and hardware state are out of sync.
4337 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
4338 * and not rely on hardware state like normal interrupts.
4340 if (unlikely(in_nmi())) {
4341 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4346 * - recursion check, because NMI can hit lockdep;
4347 * - hardware state check, because above;
4348 * - chain_key check, see lockdep_hardirqs_on_prepare().
4353 if (unlikely(this_cpu_read(lockdep_recursion)))
4356 if (lockdep_hardirqs_enabled()) {
4358 * Neither irq nor preemption are disabled here
4359 * so this is racy by nature but losing one hit
4360 * in a stat is not a big deal.
4362 __debug_atomic_inc(redundant_hardirqs_on);
4367 * We're enabling irqs and according to our state above irqs weren't
4368 * already enabled, yet we find the hardware thinks they are in fact
4369 * enabled.. someone messed up their IRQ state tracing.
4371 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4375 * Ensure the lock stack remained unchanged between
4376 * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
4378 DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
4379 current->curr_chain_key);
4382 /* we'll do an OFF -> ON transition: */
4383 __this_cpu_write(hardirqs_enabled, 1);
4384 trace->hardirq_enable_ip = ip;
4385 trace->hardirq_enable_event = ++trace->irq_events;
4386 debug_atomic_inc(hardirqs_on_events);
4388 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
4391 * Hardirqs were disabled:
4393 void noinstr lockdep_hardirqs_off(unsigned long ip)
4395 if (unlikely(!debug_locks))
4399 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
4400 * they will restore the software state. This ensures the software
4401 * state is consistent inside NMIs as well.
4404 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4406 } else if (__this_cpu_read(lockdep_recursion))
4410 * So we're supposed to get called after you mask local IRQs, but for
4411 * some reason the hardware doesn't quite think you did a proper job.
4413 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4416 if (lockdep_hardirqs_enabled()) {
4417 struct irqtrace_events *trace = ¤t->irqtrace;
4420 * We have done an ON -> OFF transition:
4422 __this_cpu_write(hardirqs_enabled, 0);
4423 trace->hardirq_disable_ip = ip;
4424 trace->hardirq_disable_event = ++trace->irq_events;
4425 debug_atomic_inc(hardirqs_off_events);
4427 debug_atomic_inc(redundant_hardirqs_off);
4430 EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
4433 * Softirqs will be enabled:
4435 void lockdep_softirqs_on(unsigned long ip)
4437 struct irqtrace_events *trace = ¤t->irqtrace;
4439 if (unlikely(!lockdep_enabled()))
4443 * We fancy IRQs being disabled here, see softirq.c, avoids
4444 * funny state and nesting things.
4446 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4449 if (current->softirqs_enabled) {
4450 debug_atomic_inc(redundant_softirqs_on);
4454 lockdep_recursion_inc();
4456 * We'll do an OFF -> ON transition:
4458 current->softirqs_enabled = 1;
4459 trace->softirq_enable_ip = ip;
4460 trace->softirq_enable_event = ++trace->irq_events;
4461 debug_atomic_inc(softirqs_on_events);
4463 * We are going to turn softirqs on, so set the
4464 * usage bit for all held locks, if hardirqs are
4467 if (lockdep_hardirqs_enabled())
4468 mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
4469 lockdep_recursion_finish();
4473 * Softirqs were disabled:
4475 void lockdep_softirqs_off(unsigned long ip)
4477 if (unlikely(!lockdep_enabled()))
4481 * We fancy IRQs being disabled here, see softirq.c
4483 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4486 if (current->softirqs_enabled) {
4487 struct irqtrace_events *trace = ¤t->irqtrace;
4490 * We have done an ON -> OFF transition:
4492 current->softirqs_enabled = 0;
4493 trace->softirq_disable_ip = ip;
4494 trace->softirq_disable_event = ++trace->irq_events;
4495 debug_atomic_inc(softirqs_off_events);
4497 * Whoops, we wanted softirqs off, so why aren't they?
4499 DEBUG_LOCKS_WARN_ON(!softirq_count());
4501 debug_atomic_inc(redundant_softirqs_off);
4505 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4511 * If non-trylock use in a hardirq or softirq context, then
4512 * mark the lock as used in these contexts:
4514 if (!hlock->trylock) {
4516 if (lockdep_hardirq_context())
4517 if (!mark_lock(curr, hlock,
4518 LOCK_USED_IN_HARDIRQ_READ))
4520 if (curr->softirq_context)
4521 if (!mark_lock(curr, hlock,
4522 LOCK_USED_IN_SOFTIRQ_READ))
4525 if (lockdep_hardirq_context())
4526 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
4528 if (curr->softirq_context)
4529 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
4533 if (!hlock->hardirqs_off) {
4535 if (!mark_lock(curr, hlock,
4536 LOCK_ENABLED_HARDIRQ_READ))
4538 if (curr->softirqs_enabled)
4539 if (!mark_lock(curr, hlock,
4540 LOCK_ENABLED_SOFTIRQ_READ))
4543 if (!mark_lock(curr, hlock,
4544 LOCK_ENABLED_HARDIRQ))
4546 if (curr->softirqs_enabled)
4547 if (!mark_lock(curr, hlock,
4548 LOCK_ENABLED_SOFTIRQ))
4554 /* mark it as used: */
4555 if (!mark_lock(curr, hlock, LOCK_USED))
4561 static inline unsigned int task_irq_context(struct task_struct *task)
4563 return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
4564 LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
4567 static int separate_irq_context(struct task_struct *curr,
4568 struct held_lock *hlock)
4570 unsigned int depth = curr->lockdep_depth;
4573 * Keep track of points where we cross into an interrupt context:
4576 struct held_lock *prev_hlock;
4578 prev_hlock = curr->held_locks + depth-1;
4580 * If we cross into another context, reset the
4581 * hash key (this also prevents the checking and the
4582 * adding of the dependency to 'prev'):
4584 if (prev_hlock->irq_context != hlock->irq_context)
4591 * Mark a lock with a usage bit, and validate the state transition:
4593 static int mark_lock(struct task_struct *curr, struct held_lock *this,
4594 enum lock_usage_bit new_bit)
4596 unsigned int new_mask, ret = 1;
4598 if (new_bit >= LOCK_USAGE_STATES) {
4599 DEBUG_LOCKS_WARN_ON(1);
4603 if (new_bit == LOCK_USED && this->read)
4604 new_bit = LOCK_USED_READ;
4606 new_mask = 1 << new_bit;
4609 * If already set then do not dirty the cacheline,
4610 * nor do any checks:
4612 if (likely(hlock_class(this)->usage_mask & new_mask))
4618 * Make sure we didn't race:
4620 if (unlikely(hlock_class(this)->usage_mask & new_mask))
4623 if (!hlock_class(this)->usage_mask)
4624 debug_atomic_dec(nr_unused_locks);
4626 hlock_class(this)->usage_mask |= new_mask;
4628 if (new_bit < LOCK_TRACE_STATES) {
4629 if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
4633 if (new_bit < LOCK_USED) {
4634 ret = mark_lock_irq(curr, this, new_bit);
4643 * We must printk outside of the graph_lock:
4646 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
4648 print_irqtrace_events(curr);
4655 static inline short task_wait_context(struct task_struct *curr)
4658 * Set appropriate wait type for the context; for IRQs we have to take
4659 * into account force_irqthread as that is implied by PREEMPT_RT.
4661 if (lockdep_hardirq_context()) {
4663 * Check if force_irqthreads will run us threaded.
4665 if (curr->hardirq_threaded || curr->irq_config)
4666 return LD_WAIT_CONFIG;
4668 return LD_WAIT_SPIN;
4669 } else if (curr->softirq_context) {
4671 * Softirqs are always threaded.
4673 return LD_WAIT_CONFIG;
4680 print_lock_invalid_wait_context(struct task_struct *curr,
4681 struct held_lock *hlock)
4685 if (!debug_locks_off())
4687 if (debug_locks_silent)
4691 pr_warn("=============================\n");
4692 pr_warn("[ BUG: Invalid wait context ]\n");
4693 print_kernel_ident();
4694 pr_warn("-----------------------------\n");
4696 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4699 pr_warn("other info that might help us debug this:\n");
4701 curr_inner = task_wait_context(curr);
4702 pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
4704 lockdep_print_held_locks(curr);
4706 pr_warn("stack backtrace:\n");
4713 * Verify the wait_type context.
4715 * This check validates we take locks in the right wait-type order; that is it
4716 * ensures that we do not take mutexes inside spinlocks and do not attempt to
4717 * acquire spinlocks inside raw_spinlocks and the sort.
4719 * The entire thing is slightly more complex because of RCU, RCU is a lock that
4720 * can be taken from (pretty much) any context but also has constraints.
4721 * However when taken in a stricter environment the RCU lock does not loosen
4724 * Therefore we must look for the strictest environment in the lock stack and
4725 * compare that to the lock we're trying to acquire.
4727 static int check_wait_context(struct task_struct *curr, struct held_lock *next)
4729 u8 next_inner = hlock_class(next)->wait_type_inner;
4730 u8 next_outer = hlock_class(next)->wait_type_outer;
4734 if (!next_inner || next->trylock)
4738 next_outer = next_inner;
4741 * Find start of current irq_context..
4743 for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
4744 struct held_lock *prev = curr->held_locks + depth;
4745 if (prev->irq_context != next->irq_context)
4750 curr_inner = task_wait_context(curr);
4752 for (; depth < curr->lockdep_depth; depth++) {
4753 struct held_lock *prev = curr->held_locks + depth;
4754 u8 prev_inner = hlock_class(prev)->wait_type_inner;
4758 * We can have a bigger inner than a previous one
4759 * when outer is smaller than inner, as with RCU.
4761 * Also due to trylocks.
4763 curr_inner = min(curr_inner, prev_inner);
4767 if (next_outer > curr_inner)
4768 return print_lock_invalid_wait_context(curr, next);
4773 #else /* CONFIG_PROVE_LOCKING */
4776 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4781 static inline unsigned int task_irq_context(struct task_struct *task)
4786 static inline int separate_irq_context(struct task_struct *curr,
4787 struct held_lock *hlock)
4792 static inline int check_wait_context(struct task_struct *curr,
4793 struct held_lock *next)
4798 #endif /* CONFIG_PROVE_LOCKING */
4801 * Initialize a lock instance's lock-class mapping info:
4803 void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
4804 struct lock_class_key *key, int subclass,
4805 u8 inner, u8 outer, u8 lock_type)
4809 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
4810 lock->class_cache[i] = NULL;
4812 #ifdef CONFIG_LOCK_STAT
4813 lock->cpu = raw_smp_processor_id();
4817 * Can't be having no nameless bastards around this place!
4819 if (DEBUG_LOCKS_WARN_ON(!name)) {
4820 lock->name = "NULL";
4826 lock->wait_type_outer = outer;
4827 lock->wait_type_inner = inner;
4828 lock->lock_type = lock_type;
4831 * No key, no joy, we need to hash something.
4833 if (DEBUG_LOCKS_WARN_ON(!key))
4836 * Sanity check, the lock-class key must either have been allocated
4837 * statically or must have been registered as a dynamic key.
4839 if (!static_obj(key) && !is_dynamic_key(key)) {
4841 printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
4842 DEBUG_LOCKS_WARN_ON(1);
4847 if (unlikely(!debug_locks))
4851 unsigned long flags;
4853 if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
4856 raw_local_irq_save(flags);
4857 lockdep_recursion_inc();
4858 register_lock_class(lock, subclass, 1);
4859 lockdep_recursion_finish();
4860 raw_local_irq_restore(flags);
4863 EXPORT_SYMBOL_GPL(lockdep_init_map_type);
4865 struct lock_class_key __lockdep_no_validate__;
4866 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
4869 print_lock_nested_lock_not_held(struct task_struct *curr,
4870 struct held_lock *hlock)
4872 if (!debug_locks_off())
4874 if (debug_locks_silent)
4878 pr_warn("==================================\n");
4879 pr_warn("WARNING: Nested lock was not taken\n");
4880 print_kernel_ident();
4881 pr_warn("----------------------------------\n");
4883 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4886 pr_warn("\nbut this task is not holding:\n");
4887 pr_warn("%s\n", hlock->nest_lock->name);
4889 pr_warn("\nstack backtrace:\n");
4892 pr_warn("\nother info that might help us debug this:\n");
4893 lockdep_print_held_locks(curr);
4895 pr_warn("\nstack backtrace:\n");
4899 static int __lock_is_held(const struct lockdep_map *lock, int read);
4902 * This gets called for every mutex_lock*()/spin_lock*() operation.
4903 * We maintain the dependency maps and validate the locking attempt:
4905 * The callers must make sure that IRQs are disabled before calling it,
4906 * otherwise we could get an interrupt which would want to take locks,
4907 * which would end up in lockdep again.
4909 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
4910 int trylock, int read, int check, int hardirqs_off,
4911 struct lockdep_map *nest_lock, unsigned long ip,
4912 int references, int pin_count)
4914 struct task_struct *curr = current;
4915 struct lock_class *class = NULL;
4916 struct held_lock *hlock;
4922 if (unlikely(!debug_locks))
4925 if (!prove_locking || lock->key == &__lockdep_no_validate__)
4928 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
4929 class = lock->class_cache[subclass];
4933 if (unlikely(!class)) {
4934 class = register_lock_class(lock, subclass, 0);
4939 debug_class_ops_inc(class);
4941 if (very_verbose(class)) {
4942 printk("\nacquire class [%px] %s", class->key, class->name);
4943 if (class->name_version > 1)
4944 printk(KERN_CONT "#%d", class->name_version);
4945 printk(KERN_CONT "\n");
4950 * Add the lock to the list of currently held locks.
4951 * (we dont increase the depth just yet, up until the
4952 * dependency checks are done)
4954 depth = curr->lockdep_depth;
4956 * Ran out of static storage for our per-task lock stack again have we?
4958 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
4961 class_idx = class - lock_classes;
4963 if (depth) { /* we're holding locks */
4964 hlock = curr->held_locks + depth - 1;
4965 if (hlock->class_idx == class_idx && nest_lock) {
4969 if (!hlock->references)
4970 hlock->references++;
4972 hlock->references += references;
4975 if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
4982 hlock = curr->held_locks + depth;
4984 * Plain impossible, we just registered it and checked it weren't no
4985 * NULL like.. I bet this mushroom I ate was good!
4987 if (DEBUG_LOCKS_WARN_ON(!class))
4989 hlock->class_idx = class_idx;
4990 hlock->acquire_ip = ip;
4991 hlock->instance = lock;
4992 hlock->nest_lock = nest_lock;
4993 hlock->irq_context = task_irq_context(curr);
4994 hlock->trylock = trylock;
4996 hlock->check = check;
4997 hlock->hardirqs_off = !!hardirqs_off;
4998 hlock->references = references;
4999 #ifdef CONFIG_LOCK_STAT
5000 hlock->waittime_stamp = 0;
5001 hlock->holdtime_stamp = lockstat_clock();
5003 hlock->pin_count = pin_count;
5005 if (check_wait_context(curr, hlock))
5008 /* Initialize the lock usage bit */
5009 if (!mark_usage(curr, hlock, check))
5013 * Calculate the chain hash: it's the combined hash of all the
5014 * lock keys along the dependency chain. We save the hash value
5015 * at every step so that we can get the current hash easily
5016 * after unlock. The chain hash is then used to cache dependency
5019 * The 'key ID' is what is the most compact key value to drive
5020 * the hash, not class->key.
5023 * Whoops, we did it again.. class_idx is invalid.
5025 if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
5028 chain_key = curr->curr_chain_key;
5031 * How can we have a chain hash when we ain't got no keys?!
5033 if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
5038 hlock->prev_chain_key = chain_key;
5039 if (separate_irq_context(curr, hlock)) {
5040 chain_key = INITIAL_CHAIN_KEY;
5043 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
5045 if (nest_lock && !__lock_is_held(nest_lock, -1)) {
5046 print_lock_nested_lock_not_held(curr, hlock);
5050 if (!debug_locks_silent) {
5051 WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
5052 WARN_ON_ONCE(!hlock_class(hlock)->key);
5055 if (!validate_chain(curr, hlock, chain_head, chain_key))
5058 curr->curr_chain_key = chain_key;
5059 curr->lockdep_depth++;
5060 check_chain_key(curr);
5061 #ifdef CONFIG_DEBUG_LOCKDEP
5062 if (unlikely(!debug_locks))
5065 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
5067 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
5068 printk(KERN_DEBUG "depth: %i max: %lu!\n",
5069 curr->lockdep_depth, MAX_LOCK_DEPTH);
5071 lockdep_print_held_locks(current);
5072 debug_show_all_locks();
5078 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
5079 max_lockdep_depth = curr->lockdep_depth;
5084 static void print_unlock_imbalance_bug(struct task_struct *curr,
5085 struct lockdep_map *lock,
5088 if (!debug_locks_off())
5090 if (debug_locks_silent)
5094 pr_warn("=====================================\n");
5095 pr_warn("WARNING: bad unlock balance detected!\n");
5096 print_kernel_ident();
5097 pr_warn("-------------------------------------\n");
5098 pr_warn("%s/%d is trying to release lock (",
5099 curr->comm, task_pid_nr(curr));
5100 print_lockdep_cache(lock);
5102 print_ip_sym(KERN_WARNING, ip);
5103 pr_warn("but there are no more locks to release!\n");
5104 pr_warn("\nother info that might help us debug this:\n");
5105 lockdep_print_held_locks(curr);
5107 pr_warn("\nstack backtrace:\n");
5111 static noinstr int match_held_lock(const struct held_lock *hlock,
5112 const struct lockdep_map *lock)
5114 if (hlock->instance == lock)
5117 if (hlock->references) {
5118 const struct lock_class *class = lock->class_cache[0];
5121 class = look_up_lock_class(lock, 0);
5124 * If look_up_lock_class() failed to find a class, we're trying
5125 * to test if we hold a lock that has never yet been acquired.
5126 * Clearly if the lock hasn't been acquired _ever_, we're not
5127 * holding it either, so report failure.
5133 * References, but not a lock we're actually ref-counting?
5134 * State got messed up, follow the sites that change ->references
5135 * and try to make sense of it.
5137 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
5140 if (hlock->class_idx == class - lock_classes)
5147 /* @depth must not be zero */
5148 static struct held_lock *find_held_lock(struct task_struct *curr,
5149 struct lockdep_map *lock,
5150 unsigned int depth, int *idx)
5152 struct held_lock *ret, *hlock, *prev_hlock;
5156 hlock = curr->held_locks + i;
5158 if (match_held_lock(hlock, lock))
5162 for (i--, prev_hlock = hlock--;
5164 i--, prev_hlock = hlock--) {
5166 * We must not cross into another context:
5168 if (prev_hlock->irq_context != hlock->irq_context) {
5172 if (match_held_lock(hlock, lock)) {
5183 static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
5184 int idx, unsigned int *merged)
5186 struct held_lock *hlock;
5187 int first_idx = idx;
5189 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
5192 for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
5193 switch (__lock_acquire(hlock->instance,
5194 hlock_class(hlock)->subclass,
5196 hlock->read, hlock->check,
5197 hlock->hardirqs_off,
5198 hlock->nest_lock, hlock->acquire_ip,
5199 hlock->references, hlock->pin_count)) {
5205 *merged += (idx == first_idx);
5216 __lock_set_class(struct lockdep_map *lock, const char *name,
5217 struct lock_class_key *key, unsigned int subclass,
5220 struct task_struct *curr = current;
5221 unsigned int depth, merged = 0;
5222 struct held_lock *hlock;
5223 struct lock_class *class;
5226 if (unlikely(!debug_locks))
5229 depth = curr->lockdep_depth;
5231 * This function is about (re)setting the class of a held lock,
5232 * yet we're not actually holding any locks. Naughty user!
5234 if (DEBUG_LOCKS_WARN_ON(!depth))
5237 hlock = find_held_lock(curr, lock, depth, &i);
5239 print_unlock_imbalance_bug(curr, lock, ip);
5243 lockdep_init_map_type(lock, name, key, 0,
5244 lock->wait_type_inner,
5245 lock->wait_type_outer,
5247 class = register_lock_class(lock, subclass, 0);
5248 hlock->class_idx = class - lock_classes;
5250 curr->lockdep_depth = i;
5251 curr->curr_chain_key = hlock->prev_chain_key;
5253 if (reacquire_held_locks(curr, depth, i, &merged))
5257 * I took it apart and put it back together again, except now I have
5258 * these 'spare' parts.. where shall I put them.
5260 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
5265 static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5267 struct task_struct *curr = current;
5268 unsigned int depth, merged = 0;
5269 struct held_lock *hlock;
5272 if (unlikely(!debug_locks))
5275 depth = curr->lockdep_depth;
5277 * This function is about (re)setting the class of a held lock,
5278 * yet we're not actually holding any locks. Naughty user!
5280 if (DEBUG_LOCKS_WARN_ON(!depth))
5283 hlock = find_held_lock(curr, lock, depth, &i);
5285 print_unlock_imbalance_bug(curr, lock, ip);
5289 curr->lockdep_depth = i;
5290 curr->curr_chain_key = hlock->prev_chain_key;
5292 WARN(hlock->read, "downgrading a read lock");
5294 hlock->acquire_ip = ip;
5296 if (reacquire_held_locks(curr, depth, i, &merged))
5299 /* Merging can't happen with unchanged classes.. */
5300 if (DEBUG_LOCKS_WARN_ON(merged))
5304 * I took it apart and put it back together again, except now I have
5305 * these 'spare' parts.. where shall I put them.
5307 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
5314 * Remove the lock from the list of currently held locks - this gets
5315 * called on mutex_unlock()/spin_unlock*() (or on a failed
5316 * mutex_lock_interruptible()).
5319 __lock_release(struct lockdep_map *lock, unsigned long ip)
5321 struct task_struct *curr = current;
5322 unsigned int depth, merged = 1;
5323 struct held_lock *hlock;
5326 if (unlikely(!debug_locks))
5329 depth = curr->lockdep_depth;
5331 * So we're all set to release this lock.. wait what lock? We don't
5332 * own any locks, you've been drinking again?
5335 print_unlock_imbalance_bug(curr, lock, ip);
5340 * Check whether the lock exists in the current stack
5343 hlock = find_held_lock(curr, lock, depth, &i);
5345 print_unlock_imbalance_bug(curr, lock, ip);
5349 if (hlock->instance == lock)
5350 lock_release_holdtime(hlock);
5352 WARN(hlock->pin_count, "releasing a pinned lock\n");
5354 if (hlock->references) {
5355 hlock->references--;
5356 if (hlock->references) {
5358 * We had, and after removing one, still have
5359 * references, the current lock stack is still
5360 * valid. We're done!
5367 * We have the right lock to unlock, 'hlock' points to it.
5368 * Now we remove it from the stack, and add back the other
5369 * entries (if any), recalculating the hash along the way:
5372 curr->lockdep_depth = i;
5373 curr->curr_chain_key = hlock->prev_chain_key;
5376 * The most likely case is when the unlock is on the innermost
5377 * lock. In this case, we are done!
5382 if (reacquire_held_locks(curr, depth, i + 1, &merged))
5386 * We had N bottles of beer on the wall, we drank one, but now
5387 * there's not N-1 bottles of beer left on the wall...
5388 * Pouring two of the bottles together is acceptable.
5390 DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
5393 * Since reacquire_held_locks() would have called check_chain_key()
5394 * indirectly via __lock_acquire(), we don't need to do it again
5400 static __always_inline
5401 int __lock_is_held(const struct lockdep_map *lock, int read)
5403 struct task_struct *curr = current;
5406 for (i = 0; i < curr->lockdep_depth; i++) {
5407 struct held_lock *hlock = curr->held_locks + i;
5409 if (match_held_lock(hlock, lock)) {
5410 if (read == -1 || !!hlock->read == read)
5411 return LOCK_STATE_HELD;
5413 return LOCK_STATE_NOT_HELD;
5417 return LOCK_STATE_NOT_HELD;
5420 static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
5422 struct pin_cookie cookie = NIL_COOKIE;
5423 struct task_struct *curr = current;
5426 if (unlikely(!debug_locks))
5429 for (i = 0; i < curr->lockdep_depth; i++) {
5430 struct held_lock *hlock = curr->held_locks + i;
5432 if (match_held_lock(hlock, lock)) {
5434 * Grab 16bits of randomness; this is sufficient to not
5435 * be guessable and still allows some pin nesting in
5436 * our u32 pin_count.
5438 cookie.val = 1 + (sched_clock() & 0xffff);
5439 hlock->pin_count += cookie.val;
5444 WARN(1, "pinning an unheld lock\n");
5448 static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5450 struct task_struct *curr = current;
5453 if (unlikely(!debug_locks))
5456 for (i = 0; i < curr->lockdep_depth; i++) {
5457 struct held_lock *hlock = curr->held_locks + i;
5459 if (match_held_lock(hlock, lock)) {
5460 hlock->pin_count += cookie.val;
5465 WARN(1, "pinning an unheld lock\n");
5468 static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5470 struct task_struct *curr = current;
5473 if (unlikely(!debug_locks))
5476 for (i = 0; i < curr->lockdep_depth; i++) {
5477 struct held_lock *hlock = curr->held_locks + i;
5479 if (match_held_lock(hlock, lock)) {
5480 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
5483 hlock->pin_count -= cookie.val;
5485 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
5486 hlock->pin_count = 0;
5492 WARN(1, "unpinning an unheld lock\n");
5496 * Check whether we follow the irq-flags state precisely:
5498 static noinstr void check_flags(unsigned long flags)
5500 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
5504 /* Get the warning out.. */
5505 instrumentation_begin();
5507 if (irqs_disabled_flags(flags)) {
5508 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
5509 printk("possible reason: unannotated irqs-off.\n");
5512 if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
5513 printk("possible reason: unannotated irqs-on.\n");
5517 #ifndef CONFIG_PREEMPT_RT
5519 * We dont accurately track softirq state in e.g.
5520 * hardirq contexts (such as on 4KSTACKS), so only
5521 * check if not in hardirq contexts:
5523 if (!hardirq_count()) {
5524 if (softirq_count()) {
5525 /* like the above, but with softirqs */
5526 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
5528 /* lick the above, does it taste good? */
5529 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
5535 print_irqtrace_events(current);
5537 instrumentation_end();
5541 void lock_set_class(struct lockdep_map *lock, const char *name,
5542 struct lock_class_key *key, unsigned int subclass,
5545 unsigned long flags;
5547 if (unlikely(!lockdep_enabled()))
5550 raw_local_irq_save(flags);
5551 lockdep_recursion_inc();
5553 if (__lock_set_class(lock, name, key, subclass, ip))
5554 check_chain_key(current);
5555 lockdep_recursion_finish();
5556 raw_local_irq_restore(flags);
5558 EXPORT_SYMBOL_GPL(lock_set_class);
5560 void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5562 unsigned long flags;
5564 if (unlikely(!lockdep_enabled()))
5567 raw_local_irq_save(flags);
5568 lockdep_recursion_inc();
5570 if (__lock_downgrade(lock, ip))
5571 check_chain_key(current);
5572 lockdep_recursion_finish();
5573 raw_local_irq_restore(flags);
5575 EXPORT_SYMBOL_GPL(lock_downgrade);
5577 /* NMI context !!! */
5578 static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
5580 #ifdef CONFIG_PROVE_LOCKING
5581 struct lock_class *class = look_up_lock_class(lock, subclass);
5582 unsigned long mask = LOCKF_USED;
5584 /* if it doesn't have a class (yet), it certainly hasn't been used yet */
5589 * READ locks only conflict with USED, such that if we only ever use
5590 * READ locks, there is no deadlock possible -- RCU.
5593 mask |= LOCKF_USED_READ;
5595 if (!(class->usage_mask & mask))
5598 hlock->class_idx = class - lock_classes;
5600 print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
5604 static bool lockdep_nmi(void)
5606 if (raw_cpu_read(lockdep_recursion))
5616 * read_lock() is recursive if:
5617 * 1. We force lockdep think this way in selftests or
5618 * 2. The implementation is not queued read/write lock or
5619 * 3. The locker is at an in_interrupt() context.
5621 bool read_lock_is_recursive(void)
5623 return force_read_lock_recursive ||
5624 !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
5627 EXPORT_SYMBOL_GPL(read_lock_is_recursive);
5630 * We are not always called with irqs disabled - do that here,
5631 * and also avoid lockdep recursion:
5633 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5634 int trylock, int read, int check,
5635 struct lockdep_map *nest_lock, unsigned long ip)
5637 unsigned long flags;
5639 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
5644 if (unlikely(!lockdep_enabled())) {
5645 /* XXX allow trylock from NMI ?!? */
5646 if (lockdep_nmi() && !trylock) {
5647 struct held_lock hlock;
5649 hlock.acquire_ip = ip;
5650 hlock.instance = lock;
5651 hlock.nest_lock = nest_lock;
5652 hlock.irq_context = 2; // XXX
5653 hlock.trylock = trylock;
5655 hlock.check = check;
5656 hlock.hardirqs_off = true;
5657 hlock.references = 0;
5659 verify_lock_unused(lock, &hlock, subclass);
5664 raw_local_irq_save(flags);
5667 lockdep_recursion_inc();
5668 __lock_acquire(lock, subclass, trylock, read, check,
5669 irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
5670 lockdep_recursion_finish();
5671 raw_local_irq_restore(flags);
5673 EXPORT_SYMBOL_GPL(lock_acquire);
5675 void lock_release(struct lockdep_map *lock, unsigned long ip)
5677 unsigned long flags;
5679 trace_lock_release(lock, ip);
5681 if (unlikely(!lockdep_enabled()))
5684 raw_local_irq_save(flags);
5687 lockdep_recursion_inc();
5688 if (__lock_release(lock, ip))
5689 check_chain_key(current);
5690 lockdep_recursion_finish();
5691 raw_local_irq_restore(flags);
5693 EXPORT_SYMBOL_GPL(lock_release);
5695 noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
5697 unsigned long flags;
5698 int ret = LOCK_STATE_NOT_HELD;
5701 * Avoid false negative lockdep_assert_held() and
5702 * lockdep_assert_not_held().
5704 if (unlikely(!lockdep_enabled()))
5705 return LOCK_STATE_UNKNOWN;
5707 raw_local_irq_save(flags);
5710 lockdep_recursion_inc();
5711 ret = __lock_is_held(lock, read);
5712 lockdep_recursion_finish();
5713 raw_local_irq_restore(flags);
5717 EXPORT_SYMBOL_GPL(lock_is_held_type);
5718 NOKPROBE_SYMBOL(lock_is_held_type);
5720 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
5722 struct pin_cookie cookie = NIL_COOKIE;
5723 unsigned long flags;
5725 if (unlikely(!lockdep_enabled()))
5728 raw_local_irq_save(flags);
5731 lockdep_recursion_inc();
5732 cookie = __lock_pin_lock(lock);
5733 lockdep_recursion_finish();
5734 raw_local_irq_restore(flags);
5738 EXPORT_SYMBOL_GPL(lock_pin_lock);
5740 void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5742 unsigned long flags;
5744 if (unlikely(!lockdep_enabled()))
5747 raw_local_irq_save(flags);
5750 lockdep_recursion_inc();
5751 __lock_repin_lock(lock, cookie);
5752 lockdep_recursion_finish();
5753 raw_local_irq_restore(flags);
5755 EXPORT_SYMBOL_GPL(lock_repin_lock);
5757 void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5759 unsigned long flags;
5761 if (unlikely(!lockdep_enabled()))
5764 raw_local_irq_save(flags);
5767 lockdep_recursion_inc();
5768 __lock_unpin_lock(lock, cookie);
5769 lockdep_recursion_finish();
5770 raw_local_irq_restore(flags);
5772 EXPORT_SYMBOL_GPL(lock_unpin_lock);
5774 #ifdef CONFIG_LOCK_STAT
5775 static void print_lock_contention_bug(struct task_struct *curr,
5776 struct lockdep_map *lock,
5779 if (!debug_locks_off())
5781 if (debug_locks_silent)
5785 pr_warn("=================================\n");
5786 pr_warn("WARNING: bad contention detected!\n");
5787 print_kernel_ident();
5788 pr_warn("---------------------------------\n");
5789 pr_warn("%s/%d is trying to contend lock (",
5790 curr->comm, task_pid_nr(curr));
5791 print_lockdep_cache(lock);
5793 print_ip_sym(KERN_WARNING, ip);
5794 pr_warn("but there are no locks held!\n");
5795 pr_warn("\nother info that might help us debug this:\n");
5796 lockdep_print_held_locks(curr);
5798 pr_warn("\nstack backtrace:\n");
5803 __lock_contended(struct lockdep_map *lock, unsigned long ip)
5805 struct task_struct *curr = current;
5806 struct held_lock *hlock;
5807 struct lock_class_stats *stats;
5809 int i, contention_point, contending_point;
5811 depth = curr->lockdep_depth;
5813 * Whee, we contended on this lock, except it seems we're not
5814 * actually trying to acquire anything much at all..
5816 if (DEBUG_LOCKS_WARN_ON(!depth))
5819 hlock = find_held_lock(curr, lock, depth, &i);
5821 print_lock_contention_bug(curr, lock, ip);
5825 if (hlock->instance != lock)
5828 hlock->waittime_stamp = lockstat_clock();
5830 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
5831 contending_point = lock_point(hlock_class(hlock)->contending_point,
5834 stats = get_lock_stats(hlock_class(hlock));
5835 if (contention_point < LOCKSTAT_POINTS)
5836 stats->contention_point[contention_point]++;
5837 if (contending_point < LOCKSTAT_POINTS)
5838 stats->contending_point[contending_point]++;
5839 if (lock->cpu != smp_processor_id())
5840 stats->bounces[bounce_contended + !!hlock->read]++;
5844 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
5846 struct task_struct *curr = current;
5847 struct held_lock *hlock;
5848 struct lock_class_stats *stats;
5850 u64 now, waittime = 0;
5853 depth = curr->lockdep_depth;
5855 * Yay, we acquired ownership of this lock we didn't try to
5856 * acquire, how the heck did that happen?
5858 if (DEBUG_LOCKS_WARN_ON(!depth))
5861 hlock = find_held_lock(curr, lock, depth, &i);
5863 print_lock_contention_bug(curr, lock, _RET_IP_);
5867 if (hlock->instance != lock)
5870 cpu = smp_processor_id();
5871 if (hlock->waittime_stamp) {
5872 now = lockstat_clock();
5873 waittime = now - hlock->waittime_stamp;
5874 hlock->holdtime_stamp = now;
5877 stats = get_lock_stats(hlock_class(hlock));
5880 lock_time_inc(&stats->read_waittime, waittime);
5882 lock_time_inc(&stats->write_waittime, waittime);
5884 if (lock->cpu != cpu)
5885 stats->bounces[bounce_acquired + !!hlock->read]++;
5891 void lock_contended(struct lockdep_map *lock, unsigned long ip)
5893 unsigned long flags;
5895 trace_lock_contended(lock, ip);
5897 if (unlikely(!lock_stat || !lockdep_enabled()))
5900 raw_local_irq_save(flags);
5902 lockdep_recursion_inc();
5903 __lock_contended(lock, ip);
5904 lockdep_recursion_finish();
5905 raw_local_irq_restore(flags);
5907 EXPORT_SYMBOL_GPL(lock_contended);
5909 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
5911 unsigned long flags;
5913 trace_lock_acquired(lock, ip);
5915 if (unlikely(!lock_stat || !lockdep_enabled()))
5918 raw_local_irq_save(flags);
5920 lockdep_recursion_inc();
5921 __lock_acquired(lock, ip);
5922 lockdep_recursion_finish();
5923 raw_local_irq_restore(flags);
5925 EXPORT_SYMBOL_GPL(lock_acquired);
5929 * Used by the testsuite, sanitize the validator state
5930 * after a simulated failure:
5933 void lockdep_reset(void)
5935 unsigned long flags;
5938 raw_local_irq_save(flags);
5939 lockdep_init_task(current);
5940 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
5941 nr_hardirq_chains = 0;
5942 nr_softirq_chains = 0;
5943 nr_process_chains = 0;
5945 for (i = 0; i < CHAINHASH_SIZE; i++)
5946 INIT_HLIST_HEAD(chainhash_table + i);
5947 raw_local_irq_restore(flags);
5950 /* Remove a class from a lock chain. Must be called with the graph lock held. */
5951 static void remove_class_from_lock_chain(struct pending_free *pf,
5952 struct lock_chain *chain,
5953 struct lock_class *class)
5955 #ifdef CONFIG_PROVE_LOCKING
5958 for (i = chain->base; i < chain->base + chain->depth; i++) {
5959 if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
5962 * Each lock class occurs at most once in a lock chain so once
5963 * we found a match we can break out of this loop.
5965 goto free_lock_chain;
5967 /* Since the chain has not been modified, return. */
5971 free_chain_hlocks(chain->base, chain->depth);
5972 /* Overwrite the chain key for concurrent RCU readers. */
5973 WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
5974 dec_chains(chain->irq_context);
5977 * Note: calling hlist_del_rcu() from inside a
5978 * hlist_for_each_entry_rcu() loop is safe.
5980 hlist_del_rcu(&chain->entry);
5981 __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
5982 nr_zapped_lock_chains++;
5986 /* Must be called with the graph lock held. */
5987 static void remove_class_from_lock_chains(struct pending_free *pf,
5988 struct lock_class *class)
5990 struct lock_chain *chain;
5991 struct hlist_head *head;
5994 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
5995 head = chainhash_table + i;
5996 hlist_for_each_entry_rcu(chain, head, entry) {
5997 remove_class_from_lock_chain(pf, chain, class);
6003 * Remove all references to a lock class. The caller must hold the graph lock.
6005 static void zap_class(struct pending_free *pf, struct lock_class *class)
6007 struct lock_list *entry;
6010 WARN_ON_ONCE(!class->key);
6013 * Remove all dependencies this lock is
6016 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
6017 entry = list_entries + i;
6018 if (entry->class != class && entry->links_to != class)
6020 __clear_bit(i, list_entries_in_use);
6022 list_del_rcu(&entry->entry);
6024 if (list_empty(&class->locks_after) &&
6025 list_empty(&class->locks_before)) {
6026 list_move_tail(&class->lock_entry, &pf->zapped);
6027 hlist_del_rcu(&class->hash_entry);
6028 WRITE_ONCE(class->key, NULL);
6029 WRITE_ONCE(class->name, NULL);
6031 __clear_bit(class - lock_classes, lock_classes_in_use);
6032 if (class - lock_classes == max_lock_class_idx)
6033 max_lock_class_idx--;
6035 WARN_ONCE(true, "%s() failed for class %s\n", __func__,
6039 remove_class_from_lock_chains(pf, class);
6040 nr_zapped_classes++;
6043 static void reinit_class(struct lock_class *class)
6045 WARN_ON_ONCE(!class->lock_entry.next);
6046 WARN_ON_ONCE(!list_empty(&class->locks_after));
6047 WARN_ON_ONCE(!list_empty(&class->locks_before));
6048 memset_startat(class, 0, key);
6049 WARN_ON_ONCE(!class->lock_entry.next);
6050 WARN_ON_ONCE(!list_empty(&class->locks_after));
6051 WARN_ON_ONCE(!list_empty(&class->locks_before));
6054 static inline int within(const void *addr, void *start, unsigned long size)
6056 return addr >= start && addr < start + size;
6059 static bool inside_selftest(void)
6061 return current == lockdep_selftest_task_struct;
6064 /* The caller must hold the graph lock. */
6065 static struct pending_free *get_pending_free(void)
6067 return delayed_free.pf + delayed_free.index;
6070 static void free_zapped_rcu(struct rcu_head *cb);
6073 * Schedule an RCU callback if no RCU callback is pending. Must be called with
6074 * the graph lock held.
6076 static void call_rcu_zapped(struct pending_free *pf)
6078 WARN_ON_ONCE(inside_selftest());
6080 if (list_empty(&pf->zapped))
6083 if (delayed_free.scheduled)
6086 delayed_free.scheduled = true;
6088 WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
6089 delayed_free.index ^= 1;
6091 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6094 /* The caller must hold the graph lock. May be called from RCU context. */
6095 static void __free_zapped_classes(struct pending_free *pf)
6097 struct lock_class *class;
6099 check_data_structures();
6101 list_for_each_entry(class, &pf->zapped, lock_entry)
6102 reinit_class(class);
6104 list_splice_init(&pf->zapped, &free_lock_classes);
6106 #ifdef CONFIG_PROVE_LOCKING
6107 bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
6108 pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
6109 bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
6113 static void free_zapped_rcu(struct rcu_head *ch)
6115 struct pending_free *pf;
6116 unsigned long flags;
6118 if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
6121 raw_local_irq_save(flags);
6125 pf = delayed_free.pf + (delayed_free.index ^ 1);
6126 __free_zapped_classes(pf);
6127 delayed_free.scheduled = false;
6130 * If there's anything on the open list, close and start a new callback.
6132 call_rcu_zapped(delayed_free.pf + delayed_free.index);
6135 raw_local_irq_restore(flags);
6139 * Remove all lock classes from the class hash table and from the
6140 * all_lock_classes list whose key or name is in the address range [start,
6141 * start + size). Move these lock classes to the zapped_classes list. Must
6142 * be called with the graph lock held.
6144 static void __lockdep_free_key_range(struct pending_free *pf, void *start,
6147 struct lock_class *class;
6148 struct hlist_head *head;
6151 /* Unhash all classes that were created by a module. */
6152 for (i = 0; i < CLASSHASH_SIZE; i++) {
6153 head = classhash_table + i;
6154 hlist_for_each_entry_rcu(class, head, hash_entry) {
6155 if (!within(class->key, start, size) &&
6156 !within(class->name, start, size))
6158 zap_class(pf, class);
6164 * Used in module.c to remove lock classes from memory that is going to be
6165 * freed; and possibly re-used by other modules.
6167 * We will have had one synchronize_rcu() before getting here, so we're
6168 * guaranteed nobody will look up these exact classes -- they're properly dead
6169 * but still allocated.
6171 static void lockdep_free_key_range_reg(void *start, unsigned long size)
6173 struct pending_free *pf;
6174 unsigned long flags;
6176 init_data_structures_once();
6178 raw_local_irq_save(flags);
6180 pf = get_pending_free();
6181 __lockdep_free_key_range(pf, start, size);
6182 call_rcu_zapped(pf);
6184 raw_local_irq_restore(flags);
6187 * Wait for any possible iterators from look_up_lock_class() to pass
6188 * before continuing to free the memory they refer to.
6194 * Free all lockdep keys in the range [start, start+size). Does not sleep.
6195 * Ignores debug_locks. Must only be used by the lockdep selftests.
6197 static void lockdep_free_key_range_imm(void *start, unsigned long size)
6199 struct pending_free *pf = delayed_free.pf;
6200 unsigned long flags;
6202 init_data_structures_once();
6204 raw_local_irq_save(flags);
6206 __lockdep_free_key_range(pf, start, size);
6207 __free_zapped_classes(pf);
6209 raw_local_irq_restore(flags);
6212 void lockdep_free_key_range(void *start, unsigned long size)
6214 init_data_structures_once();
6216 if (inside_selftest())
6217 lockdep_free_key_range_imm(start, size);
6219 lockdep_free_key_range_reg(start, size);
6223 * Check whether any element of the @lock->class_cache[] array refers to a
6224 * registered lock class. The caller must hold either the graph lock or the
6227 static bool lock_class_cache_is_registered(struct lockdep_map *lock)
6229 struct lock_class *class;
6230 struct hlist_head *head;
6233 for (i = 0; i < CLASSHASH_SIZE; i++) {
6234 head = classhash_table + i;
6235 hlist_for_each_entry_rcu(class, head, hash_entry) {
6236 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
6237 if (lock->class_cache[j] == class)
6244 /* The caller must hold the graph lock. Does not sleep. */
6245 static void __lockdep_reset_lock(struct pending_free *pf,
6246 struct lockdep_map *lock)
6248 struct lock_class *class;
6252 * Remove all classes this lock might have:
6254 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
6256 * If the class exists we look it up and zap it:
6258 class = look_up_lock_class(lock, j);
6260 zap_class(pf, class);
6263 * Debug check: in the end all mapped classes should
6266 if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
6271 * Remove all information lockdep has about a lock if debug_locks == 1. Free
6272 * released data structures from RCU context.
6274 static void lockdep_reset_lock_reg(struct lockdep_map *lock)
6276 struct pending_free *pf;
6277 unsigned long flags;
6280 raw_local_irq_save(flags);
6281 locked = graph_lock();
6285 pf = get_pending_free();
6286 __lockdep_reset_lock(pf, lock);
6287 call_rcu_zapped(pf);
6291 raw_local_irq_restore(flags);
6295 * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
6296 * lockdep selftests.
6298 static void lockdep_reset_lock_imm(struct lockdep_map *lock)
6300 struct pending_free *pf = delayed_free.pf;
6301 unsigned long flags;
6303 raw_local_irq_save(flags);
6305 __lockdep_reset_lock(pf, lock);
6306 __free_zapped_classes(pf);
6308 raw_local_irq_restore(flags);
6311 void lockdep_reset_lock(struct lockdep_map *lock)
6313 init_data_structures_once();
6315 if (inside_selftest())
6316 lockdep_reset_lock_imm(lock);
6318 lockdep_reset_lock_reg(lock);
6322 * Unregister a dynamically allocated key.
6324 * Unlike lockdep_register_key(), a search is always done to find a matching
6325 * key irrespective of debug_locks to avoid potential invalid access to freed
6326 * memory in lock_class entry.
6328 void lockdep_unregister_key(struct lock_class_key *key)
6330 struct hlist_head *hash_head = keyhashentry(key);
6331 struct lock_class_key *k;
6332 struct pending_free *pf;
6333 unsigned long flags;
6338 if (WARN_ON_ONCE(static_obj(key)))
6341 raw_local_irq_save(flags);
6344 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
6346 hlist_del_rcu(&k->hash_entry);
6351 WARN_ON_ONCE(!found && debug_locks);
6353 pf = get_pending_free();
6354 __lockdep_free_key_range(pf, key, 1);
6355 call_rcu_zapped(pf);
6358 raw_local_irq_restore(flags);
6360 /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
6363 EXPORT_SYMBOL_GPL(lockdep_unregister_key);
6365 void __init lockdep_init(void)
6367 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
6369 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
6370 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
6371 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
6372 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
6373 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
6374 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
6375 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
6377 printk(" memory used by lock dependency info: %zu kB\n",
6378 (sizeof(lock_classes) +
6379 sizeof(lock_classes_in_use) +
6380 sizeof(classhash_table) +
6381 sizeof(list_entries) +
6382 sizeof(list_entries_in_use) +
6383 sizeof(chainhash_table) +
6384 sizeof(delayed_free)
6385 #ifdef CONFIG_PROVE_LOCKING
6387 + sizeof(lock_chains)
6388 + sizeof(lock_chains_in_use)
6389 + sizeof(chain_hlocks)
6394 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
6395 printk(" memory used for stack traces: %zu kB\n",
6396 (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
6400 printk(" per task-struct memory footprint: %zu bytes\n",
6401 sizeof(((struct task_struct *)NULL)->held_locks));
6405 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
6406 const void *mem_to, struct held_lock *hlock)
6408 if (!debug_locks_off())
6410 if (debug_locks_silent)
6414 pr_warn("=========================\n");
6415 pr_warn("WARNING: held lock freed!\n");
6416 print_kernel_ident();
6417 pr_warn("-------------------------\n");
6418 pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
6419 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
6421 lockdep_print_held_locks(curr);
6423 pr_warn("\nstack backtrace:\n");
6427 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
6428 const void* lock_from, unsigned long lock_len)
6430 return lock_from + lock_len <= mem_from ||
6431 mem_from + mem_len <= lock_from;
6435 * Called when kernel memory is freed (or unmapped), or if a lock
6436 * is destroyed or reinitialized - this code checks whether there is
6437 * any held lock in the memory range of <from> to <to>:
6439 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
6441 struct task_struct *curr = current;
6442 struct held_lock *hlock;
6443 unsigned long flags;
6446 if (unlikely(!debug_locks))
6449 raw_local_irq_save(flags);
6450 for (i = 0; i < curr->lockdep_depth; i++) {
6451 hlock = curr->held_locks + i;
6453 if (not_in_range(mem_from, mem_len, hlock->instance,
6454 sizeof(*hlock->instance)))
6457 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
6460 raw_local_irq_restore(flags);
6462 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
6464 static void print_held_locks_bug(void)
6466 if (!debug_locks_off())
6468 if (debug_locks_silent)
6472 pr_warn("====================================\n");
6473 pr_warn("WARNING: %s/%d still has locks held!\n",
6474 current->comm, task_pid_nr(current));
6475 print_kernel_ident();
6476 pr_warn("------------------------------------\n");
6477 lockdep_print_held_locks(current);
6478 pr_warn("\nstack backtrace:\n");
6482 void debug_check_no_locks_held(void)
6484 if (unlikely(current->lockdep_depth > 0))
6485 print_held_locks_bug();
6487 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
6490 void debug_show_all_locks(void)
6492 struct task_struct *g, *p;
6494 if (unlikely(!debug_locks)) {
6495 pr_warn("INFO: lockdep is turned off.\n");
6498 pr_warn("\nShowing all locks held in the system:\n");
6501 for_each_process_thread(g, p) {
6502 if (!p->lockdep_depth)
6504 lockdep_print_held_locks(p);
6505 touch_nmi_watchdog();
6506 touch_all_softlockup_watchdogs();
6511 pr_warn("=============================================\n\n");
6513 EXPORT_SYMBOL_GPL(debug_show_all_locks);
6517 * Careful: only use this function if you are sure that
6518 * the task cannot run in parallel!
6520 void debug_show_held_locks(struct task_struct *task)
6522 if (unlikely(!debug_locks)) {
6523 printk("INFO: lockdep is turned off.\n");
6526 lockdep_print_held_locks(task);
6528 EXPORT_SYMBOL_GPL(debug_show_held_locks);
6530 asmlinkage __visible void lockdep_sys_exit(void)
6532 struct task_struct *curr = current;
6534 if (unlikely(curr->lockdep_depth)) {
6535 if (!debug_locks_off())
6538 pr_warn("================================================\n");
6539 pr_warn("WARNING: lock held when returning to user space!\n");
6540 print_kernel_ident();
6541 pr_warn("------------------------------------------------\n");
6542 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
6543 curr->comm, curr->pid);
6544 lockdep_print_held_locks(curr);
6548 * The lock history for each syscall should be independent. So wipe the
6549 * slate clean on return to userspace.
6551 lockdep_invariant_state(false);
6554 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
6556 struct task_struct *curr = current;
6557 int dl = READ_ONCE(debug_locks);
6559 /* Note: the following can be executed concurrently, so be careful. */
6561 pr_warn("=============================\n");
6562 pr_warn("WARNING: suspicious RCU usage\n");
6563 print_kernel_ident();
6564 pr_warn("-----------------------------\n");
6565 pr_warn("%s:%d %s!\n", file, line, s);
6566 pr_warn("\nother info that might help us debug this:\n\n");
6567 pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s",
6568 !rcu_lockdep_current_cpu_online()
6569 ? "RCU used illegally from offline CPU!\n"
6571 rcu_scheduler_active, dl,
6572 dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
6575 * If a CPU is in the RCU-free window in idle (ie: in the section
6576 * between ct_idle_enter() and ct_idle_exit(), then RCU
6577 * considers that CPU to be in an "extended quiescent state",
6578 * which means that RCU will be completely ignoring that CPU.
6579 * Therefore, rcu_read_lock() and friends have absolutely no
6580 * effect on a CPU running in that state. In other words, even if
6581 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
6582 * delete data structures out from under it. RCU really has no
6583 * choice here: we need to keep an RCU-free window in idle where
6584 * the CPU may possibly enter into low power mode. This way we can
6585 * notice an extended quiescent state to other CPUs that started a grace
6586 * period. Otherwise we would delay any grace period as long as we run
6589 * So complain bitterly if someone does call rcu_read_lock(),
6590 * rcu_read_lock_bh() and so on from extended quiescent states.
6592 if (!rcu_is_watching())
6593 pr_warn("RCU used illegally from extended quiescent state!\n");
6595 lockdep_print_held_locks(curr);
6596 pr_warn("\nstack backtrace:\n");
6599 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);